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Windows XP Boot Process
70-270: MCSE Guide toMicrosoft Windows XP Professional
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Booting Windows XP (Page 1)
Boot processphases:
Boot phase begins when computer is firstpowered on
Or begins when Restart is chosen from"Shut Down Windows" dialog box
Windows XP load phases
Begins when boot phase is completed Configuration is selected
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Booting Windows XP (Page 2)
Boot Phase Steps
Power-on self test(POST)
Initial startup
Boot loader
Select operatingsystem
Detect hardware
Select configuration
Windows XP Load Phase
Load the kernel
Initialize the kernel
Services load
Windows XP systemstartup
Log on
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Power-on Self Test (Page 1)
First step in boot sequence (the POST) forany computer with an operating system
Determines: Amount of real memory that exists
Whether or not all necessary hardwarecomponents are present and functioning
The specific tests vary depending on howthe BIOS (Basic Input/Output System) isconfigured
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Power-on Self Test (Page 2)
If POST is successful, computer boots itself
If the tests are unsuccessful, the computer
reports error by: Emitting a series of beeps (number of beeps
identifies the errordiffers from one BIOS toanother)
Also possibly might display error messageand a code on the screen
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Power-on Self Test (Page 3)
Software that performs POST resides incalled the CMOS (complementary metaloxide semiconductor)
Battery-powered chip that also can hold
basic configuration information so POSTcan check installed RAM, number and typeof hard drives, type of keyboard and mouse,the boot sequence (Which drive first?), etc.
In Windows XP, BIOS no longer storesinformation about devices and drivers
connected to system (replaced by the HAL)
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Power-on Self Test
The following screen shows results ofsample successful POST completion
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Power-on Self Test
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Power-on Self Test (Page 4)
After POST completes, each adapter witha BIOS performs its own self-test (POST),i.e.
Video card
SCSI (small computer system interface)cards which are interfaces that provide
much faster data transmission rates thanstandard parallel and serial ports; used for
printers, scanners, etc.
Adapters issue their own reports on monitor
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Power-on Self Test (Page 5)
At this point there still is no operatingsystem in RAM
POST application in the BIOS is in control
Output on screen is in basic, text-only form
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Initial Startup (Page 1)
The BIOS finds the first sector of the firsthard drive which contains the Master BootRecord (MBR) and transfers control to it:
It is the job of MBR ultimately to load the
Ntldr program (the boot loader program)and pass control of the boot process on toit (either directly or indirectly)
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Initial Startup (Page 2)
The Master Boot Record (con.):
In FAT partitions, because the boot sectoris only one sector in size, MBR points toanother location on disk which then pointsto the boot loader
In NTFS partitions, boot sectors may be upto 16 sectors in size so it is large enough tostore the code to find the boot loader
If booting from a floppy, the first sectorcontains the partition boot sector
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Initial Startup (Page 3)
BIOS stores information as to the order inwhich drives are checked to see which isthe startup drive (as stored in CMOS)
If floppy drive is in the sequence, partition
boot sector is loaded and runs the MBRfrom the floppy
If the floppy does not have a partition bootsector, the message "Non-system disk or
disk error " appears
Remove disk, and turn machine off an then
ondo not rebootto avoid viruses
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Initial Startup (Page 3)
Ntldr is stored on the system partition
This is the partition where the MBRexpects to find the system
Ultimately its job is to boot the WindowsXP operating system which is stored onthe boot partition
The system itself actually can be storedon any partition
The system and boot partitions may ormay not be the same
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Boot Loader (Page 1)
Collection of files on system partition usedto initiate loading of operating system
Required files to boot Windows XP areNtldr, Ntdetect.com and Boot.ini
Other optional boot loader programs areBootsect.dos and Ntbootdd.sys
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Windows XP Startup Files
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Boot Loader (Page 2)
The boot loader first switches processorinto 32-bit mode
Previously it had been running in real modeas if it were an 8088 or 8086 machine
Next it starts the appropriate file system,FAT, FAT32 or NTFS
The ability to access any of the file systemsis programmed into Ntldr
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Boot Loader (Page 3)
Primary functions of the boot loader are to:
1. Select the operating system to load if thereis more than one from which to choose
2. Detect hardware
3. Select a configuration
Ntldr stays in control throughout boot
loader process until it loads and passescontrol to Windows XP kernel (Ntoskrnl.ext)
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Selecting the Operating System
Ntldr reads Boot.ini and displays the Bootselection menu (if necessary)
Contains operating system choices, if morethat one, from which the user may choose
It also is possible from this screen to press to reach the "Troubleshooting and
Advanced Startup" screen (more later) Will auto select first option after a specified
number of seconds
Change default O/S or time in Boot.ini
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Boot Selection Menu
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Detecting Hardware
If the user selects Windows XP (or if it isthe only O/S present), Ntldr executesNtdetect.com
Used to collect a list of hardware currently
installed in computer
From hardware list, creates system profile
Later will be compared to Windows XPRegistry entries for discrepancies thatcould lead to problems
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Selecting a Configuration
Next boot loader selects a configuration
Known as the hardware profile
If there is one hardware profile, it is selected If there is more than one, system tries to
select one that matches detected hardware
If system cannot make automatic selection,
user is prompted for manual selection
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Troubleshooting and Advanced
Startup Options (Page 1)
Windows XP combines the boot andrecovery options of Windows NT andWindows 95/98
Provides several options to restore amalfunctioning system to functional state
Before timer expires, or Windows XP
kernel starts to load, press toaccess Windows Advanced Options Menu
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Troubleshooting and Advanced
Startup Options
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Troubleshooting and Advanced
Startup Options (Page 2)
Contents of menu may include:
Safe Modeboots Windows XP with onlyminimum system files and drivers
May be able to boot into a functioningsystem when some drivers are corrupted
Might allow replacing or removing theproblem driver before rebooting
Safe Mode with Networkingsame as
above but with networking components
If network drivers are not the problem
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Troubleshooting and Advanced
Startup Options (Page 3)
Contents of menu may include (con.):
Safe Mode with Command Promptsameas above but not to the GUI environment
Enable Boot Loggingenables or disables
boot process, and writes details to log fileNtbtlog.txt in %systemroot% folder
Records process of steps between bootmenu and logon prompt which couldprovide clues to which driver, system orprocedure is causing the problem
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Troubleshooting and Advanced
Startup Options (Page 4)
Contents of menu may include (con.):
Enable VGA Modenormal boot but withonly basic VGA video driver (in case there
is a bad video driver)
Last Known Good Configurationstate ofRegistry during last successful user logon
Could be useful if a new driver or softwarerecently has been installed, or the Registrywas recently modified
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Troubleshooting and Advanced
Startup Options (Page 5)
Contents of menu may include (con.):
Directory Services Restore Modeonly onWindows XP domain controllers, restores
Active Directory
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Troubleshooting and Advanced
Startup Options (Page 6)
Contents of menu may include (con.):
Debugging Modenormal boot but sendsdebugging information to another system
over a serial cable
If no other option helps in restoring system,may help determine where in boot processthe problem occurs
Complex information usually used by high-end programmersconsult MicrosoftWindows XP Professional Resource Kit
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*** Activity ***
Try one or more of following boot options(press function key during boot):
Safe Mode
Safe Mode with Command Prompt
Enable VGA Mode
Last Known Good Configuration
Reboot normally when done
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Boot Configuration and Selecting
an Operating System (Page 1)
Controlled through configuration of theBoot.inifile
Located in the root directory of the systempartition (usually drive C:\)
To view the file, uncheck "Hide Protectedoperating system files" in Folder Options
Updated from the "System and Recovery"dialog window on the Advanced tab ofControl Panel's System applet
To Sample"Boot.ini"
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Boot Configuration and Selecting
an Operating System (Page 2)
Used by boot loader to display the list ofavailable operating systems
Consists of two sections: [boot loader] and[operating systems]
To Sample"Boot.ini"
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Sample "Boot.ini"
Return
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Settings:
Timeoutnumber of seconds system waitsfor user to select an operating system
If set to zero (0), the default operating
system is loaded automatically
If set to (-1), waits indefinitely (this value
only can be set in text editoran invalidvalue in System applet in "Control Panel"
Defaultshows path to default O/S
[boot loader]
To Sample"Boot.ini"
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[operating systems] (Page 1)
Lists available operating systems asfollows:
Path to boot partition for operating system
Text displayed in boot loader screen
Optional parameters (switches) provideoptions many of which are equivalent to
"Windows Advanced Options Menus"As well as a few other options
To Sample"Boot.ini"
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[operating systems] (Page 2)
Switches:
/BASEVIDEOsame as Enable VGA Mode
/BAUDRATE=nbaud rate for DebuggingMode
/BOOTLOGsame as Enable Boot Logging
/CRASHDEBUGstarts Debugging Mode but
remains inactive until STOP error occurs
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[operating systems] (Page 3)
Switches (con.):
/DEBUGstarts Debugging Mode andallows access by the remote computer
/DEBUGPORT={com1|com2|1394}sets
port for Debugging Mode
/FASTDETECT={com1|com2|}specifies
serial ports to skip during hardware scanAll if no port specified
Included in every entry by default when theoperating system is installed
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[operating systems] (Page 4)
Switches (con.):
/MAXMEM=nsets maximum RAM O/Scan use
/NOGUIBOOTboots without showing
splash screen
/NODEBUGdisables Debugging Mode
/NUMPROC=nsets maximum number ofprocessors on multiprocessor machine thatO/S may use
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[operating systems] (Page 5)
Switches (con.):
/SAFEBOOT:MINIMALboots to Safe Mode
/SAFEBOOT:NETWORKboots to SafeMode with Networking
/SAFEBOOT:MINIMAL(ALTERNATESHELL)boots to Safe Mode with Command
Prompt/SOSdisplays device driver names when
they are loaded
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Advanced RISC Computing
Pathnames (Page 1)
Advanced RISC Computing pathnameis a path naming convention that is usedin the "Boot.ini" file
Defines the hard disk, partition and folderwhere Windows XP Professional and anyother operating systems reside
Created automatically when an operatingsystem is installed into a partition
To Sample"Boot.ini"
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Advanced RISC Computing
Pathnames (Page 2)
The parts of the path are:
scsi(n) or multi(n)whether the drive typeis SCSI or other (multi) and the adapter
number
disk(n)the SCSI bus number
rdisk(n)which disk contains the O/S
partition(n)selects partition with the O/S\pathselect path with the O/S
To Sample"Boot.ini"
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Editing Boot.ini
Options for editing (see next slides):
Use Control Panel to edit indirectly
Use text editor (i.e. Notepad) to changethe Boot.ini file directly
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Using Control Panel
Safest way to proceed
Select System applet in "Control Panel",then select Advanced tab, and the Startupand Recovery button
Options to modify:
Choose "Default operating system" (the
default boot selection) Select "Time to display list of operating
systems" (delay interval before bootselection starts automatically)
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Startup and Recover Dialog
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Using a Text Editor
Use Notepad or any other text editor
The button in the "Startup andRecovery" window launches Notepad
and opens the Boot.ini file
Be careful when editing file
Windows XP might not boot if there is an
incorrect configuration Create backup copy of the file before
making changes
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*** Activity ***
Before starting this activity, you shouldbackup boot.ini
Modify "timeout" value using Notepad
Set the "timeout" value back to its originalvalue (30) using Startup and Recoverydialog in System applet in "Control Panel"
Return to Notepad and open boot.ini toconfirm the change
S t lid
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*** Activity ***
Before starting this activity, you shouldbackup boot.ini
In Notepad, create one or more additionaloperating system entries, i.e.
An additional Windows XP Professionalentry but booting in VGA Mode
A fictionalentry for Windows 2000 on analternate partition
See next slide
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Sample "Boot.ini"
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="MicrosoftWindows XP Professional" /fastdetect
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft
Windows XP Pro VGA Mode" /fastdetect/basevideo
multi(0)disk(0)rdisk(3)partition(2)\WINNT="MicrosoftWindows 2000" /fastdetect
To Sample"Boot.ini"
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Windows XP Load Phase
Stages:
Loading the kernel
Initializing the kernel
Services load
Windows XP system startup
Logging on
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Loading the Kernel (Page 1)
Once Windows XP is selected as O/S toboot, a "Starting Windows" text message
and the XP splash screen are displayed
During this time the boot loader loads thekernel into memory (consists of):
Windows XP kernel (Ntoskrnl.exe)
Hardware abstraction layer (HAL), the filethat is named Hal.dll
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Loading the Kernel (Page 2)
The kernel is the centralmodule of an operating system:
Loads first and remains in
main memory at all times
Essential that it is as small aspossible while still providingservices required by the O/Sand applications
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Loading the Kernel (Page 3)
The kernel (con.)
Communicates between processes andthe hardware
Responsible for memory management,
process and task management, and diskmanagement
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Loading the Kernel (Page 4)
The Hardware Abstraction Layer (HAL)is an O/S programming component
Functions as an interface between the
systems hardware and software
Applications do not access hardwaredirectly but access the abstract layerprovided by the HAL
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Loading the Kernel (Page 5)
Hardware Abstraction Layer (con.):
Like APIs, allows applications to be device-independent
They abstract information from systemssuch as caches, I/O buses and interrupts
Use this data to give the software a way tointeract with the specific requirementsof
the hardware on which it is running
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Loading the Kernel (Page 6)
Before kernel and HAL begin to execute,the boot loader loads the Registry keyHKLM\SYSTEM
Retrieves configuration based upon Registrysubkey HKLM\SYSTEM\Select data value
CurrentControlSet is created (not written toRegistry yet) from one of the following:
ControlSet00x, a per either the Select orLastKnownGoodRecovery(if Last KnownGood Configuration was selected) data
value, Default, etc.
See next slide (HKLM\SYSTEM\Select)
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Loading the Kernel
Return
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Loading the Kernel (Page 7)
Loads driverslisted in Registry subkey:
HKLM\SYSTEM\CurrentControlSet\Services
These drivers are loaded and/or initializedaccording to their Registry settings
See next slide (HKLM\SYSTEM\CurrentControlSet\Services
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Initializing the Kernel (Page 1)
Registry key HKLM\HARDWARE createdby kernel using information it receivedfrom boot loader program Ntdetect.com
Creates CloneControlSet by making acopy of CurrentControlSet
Never modifiedintended as a backup
Initializes drivers that were loaded by theboot loader
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Initializing the Kernel (Page 2)
If the driver experiences an error whileloading, a message with the error levelreported is reported to the kernel:
Ignoreerror is ignored and no message isdisplayed to user
Normalboot process continues withmessage displayed to user
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Initializing the Kernel (Page 3)
Driver error levels (con.):
Severedisplays message; if Last KnownGood Configuration is not in use, restarts
using LKGC; if LKGC is in use, bootprocess continuesafter message
Criticaldisplays message; if Last KnownGood Configuration is not in use, restarts
using LKGC; if LKGC is in use, bootprocess failsafter message
All events saved to the System log
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Services Load (Page 1)
Kernel starts Session Manager
Starts programs that correspond to keyentries under Registry key:
HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\BootExecute
A REG_MULTI_SZ data type, i.e. an array
The default entry Autocheck makes surethese files are consistent, and tries torepair them if they are not
See next slide (HKLM\SYSTEM\CurrentControlSet\Control\SessionManager\BootExecute
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Services Load
Return
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Services Load (Page 2)
Paging files are set up as per:
HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management
See next slide (HKLM\SYSTEM\CurrentControlSet\Control\SessionManager\Memory Management
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Services Load
Return
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Services Load (Page 3)
Session Manager writes to Registry:
CurrentControlSet
CloneControlSet
Windows (Win32) subsystem loaded asper Registry entry:
HKLM\SYSTEM\CurrentControlSet\Control\
Session Manager\Subsystems Default subsystem, and also the subsystem
in which the user shell always executes
See next slide (HKLM\SYSTEM\CurrentControlSet\Control\SessionManager\Subsystems
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Services Load
Return
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Windows XP System Startup
At this point, Windows is considered fullystarted which is signaled by appearance ofa Windows XP logon screen
Win32 subsystem starts winlogon.exewhich launches Local Security Authority(Lsass.exe) process
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Logging On
The user logs on successfully with logonname, as well as a password if required
Clone control set is copied to the Last
Known Good control set completing theboot process
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Multiple-boot Systems (Page 1)
Windows XP operating system can coexistpeacefully with other operating systems
Operating system uses one or more file
systems to organize the data withinvolumes, i.e. FAT or NTFS
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Multiple-boot Systems (Page 2)
Not all file systems and operating systemsare compatible:
MS-DOS, Windows 95/98, Windows NT,
Windows 2000, Windows Server 2003 andWindows XP can share files through FATvolumes
Windows NT, Windows 2000, Windows
Server 2003 and Windows XP can sharefiles through NTFS volumes
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Multiple-boot Systems (Page 3)
File system and operating systemcompatibility (con.):
Windows and UNIX do not have a common
file system, but Linux can access FATvolumes
Only Windows 2000, Windows Server 2003and Windows XP support dynamic disks
When selecting file systems for partitionsin a multiple-boot system, keep thesefactors in mind if you wish to share files
between the partitions
Multiple Windows Operating
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Multiple Windows Operating
Systems (Page 1)
Different versions of Windows can beinstalled on the same system, i.e.
Windows 3.1, Windows 3.11, Windows
95/98, Windows NT, Windows 2000,Windows Server 2003, even Linux/Unix
Even the same version of Windows XPcan be installed on separate partitions
Multiple Windows Operating
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Multiple Windows Operating
Systems (Page 2)
Why? User needs to run software versionsthat require an older O/S
Just remember to specify different partitions
for each installation
To run an application under two O/Ss, run
the setup program twice, once while booted
to each operating system
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Multiple Installation Order
Order in which you install operatingsystems is important
Install older operating systems first, i.e.
MS-DOS, Windows 95/98, Windows2000/2003, etc.
This really is a warning, not necessarily an
absolute requirement When installing Windows XP, it recognizes
the previously installed older O/S andleaves it alone
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