Look here..its rather lengthy..
How to Enable 48-bit Logical Block Addressing Support for ATAPI Disk Drives
in Windows XP
The information in this article applies to:
a.. Microsoft Windows XP Professional
b.. Microsoft Windows XP Home Edition
This article was previously published under Q303013
IMPORTANT: This article contains information about modifying the registry.
Before you modify the registry, make sure to back it up and make sure that
you understand how to restore the registry if a problem occurs. For
information about how to back up, restore, and edit the registry, click the
following article number to view the article in the Microsoft Knowledge
Base:
256986 Description of the Microsoft Windows Registry
SUMMARY
This article describes the Windows XP 48-bit Logical Block Addressing (LBA)
support for ATA Packet Interface (ATAPI) disk drives that can enable the
capacity of your hard disk to exceed the current 137 gigabyte (GB) limit.
NOTE: 48-bit LBA support will not be enabled and therefore supported until
Service Pack 1 (SP1) for Windows XP Home Edition or Windows XP Professional
is officially released and installed. Manually enabling 48-bit LBA support
on Windows XP Without SP1 installed could lead to potential data loss.
For additional information about the latest service pack for Windows XP,
click the article number below to view the article in the Microsoft
Knowledge Base:
322389 How to Obtain the Latest Windows XP Service Pack
MORE INFORMATION
WARNING: If you use Registry Editor incorrectly, you may cause serious
problems that may require you to reinstall your operating system. Microsoft
cannot guarantee that you can solve problems that result from using Registry
Editor incorrectly. Use Registry Editor at your own risk.
Windows XP includes 48-bit LBA support for ATAPI disk drives that can enable
the capacity of your hard disk to exceed the current 137 GB limit. This type
of support is new technology and Microsoft has only tested a limited number
of these disk drives. By default, Windows XP Home Edition and Windows XP
Professional do not have 48-bit LBA support enabled.
You must meet the following requirements to use 48-bit LBA ATAPI support:
a.. You must have a 48-bit LBA compatible BIOS.
b.. You must have a hard disk that has a capacity that is greater than 137
GB.
c.. You must have Windows XP installed.
d.. For Windows XP Home Edition or Windows XP Professional, you must
enable the support in the registry by adding or changing the registry value,
EnableBigLba, to 1 in the following registry:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Atapi\Parameters\
WARNING: By default 48-bit LBA ATAPI support on Windows XP Home Edition and
Professional is unavailable. Users must add the registry key mentioned
earlier to make this addressing available to access disk space beyond the
first 137GB. Data corruption can occur if previous versions of Windows that
do not support 48-bit LBA out of the box (for example, Windows 2000 or
earlier) are installed on a disk partition that was previously created by a
48-bit aware operating system such as Windows XP that is greater in size or
spans the current addressable limit of 137GB. NOTE: This includes Windows XP
RTM versions. By default, the behavior does not occur in Windows XP RTM.
Also note that if you manually turn on 48-bit LBA support on Windows XP
without Service Pack 1 installed, you may cause data loss.
To enable 48-bit LBA large-disk support in the registry:
1.. Start Registry Editor (Regedt32.exe).
2.. Locate and click the following key in the registry:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Atapi\Parameters\
3.. On the Edit menu, click Add Value, and then add the following registry
value:
Value name: EnableBigLba
Data type: REG_DWORD
Value data: 0x1
4.. Quit Registry Editor.
WARNING: By default 48-bit LBA ATAPI support on Windows XP Home Edition and
Professional is unavailable. Users must add the registry key mentioned
earlier to make this addressing available to access disk space beyond the
first 137GB. Data corruption can occur if previous versions of Windows that
do not support 48-bit LBA out of the box (for example, Windows 2000 or
earlier) are installed on a disk partition that was previously created by a
48-bit aware operating system such as Windows XP that is greater in size or
spans the current addressable limit of 137GB. NOTE: This includes Windows XP
RTM versions. By default, the behavior does not occur in Windows XP RTM.
Also note that if you manually turn on 48-bit LBA support on Windows XP
without Service Pack 1 installed, you may cause data loss.
NOTE: If you attempt to enable the 48-bit LBA ATAPI support by editing the
preceding registry setting and you did not meet the minimum requirements,
you may observe the following behavior:
a.. The registry value, EnableBigLba, is disabled:
If you have a 48-bit compatible BIOS that can support a hard disk that has
a capacity that is greater than 137 GB, only the first 137 GB of the hard
disk are addressable. The remainder of the hard disk is not used.
b.. The registry value, EnableBigLba, is enabled, but you do not have a
48-bit LBA compatible BIOS and the capacity of the hard disk does not exceed
137 GB:
If you enable the 48-bit LBA ATAPI support by editing the registry
setting, but you lack both a 48-bit LBA compatible BIOS and a hard disk that
has a capacity that is greater than 137 GB, you have not changed the system.
The hard disk continues to function as a standard hard disk.
c.. The registry value, EnableBigLba, is enabled without a 48-bit LBA
compatible BIOS, but you have a hard disk with a capacity that is larger
than 137 GB:
If you enable 48-bit ATAPI support in the registry and you have a hard
disk that has a capacity that is greater than 137 GB, but you do not have a
48-bit LBA compatible BIOS, only the first 137 GB of the hard disk are
addressable. The remainder of the hard disk is not used.
To enable 48-bit LBA support by means of an unattended installation with the
Microsoft System Preparation (Sysprep) tool:
1.. Copy the following text into Microsoft Windows Notepad and save the
text as the 48bitLba.inf file:
[version]
signature="$CHICAGO$"
SetupClass=BASE
[DefaultInstall]
AddReg=48bitlba.Add.Reg
[48bitlba.Add.Reg]
HKLM,"System\CurrentControlSet\Services\Atapi\Parameters","EnableBigLba",0x1
0001,12.. Create a file named Cmdlines.txt, which includes the following
lines:
[Commands]
"rundll32 setupapi,InstallHinfSection DefaultInstall 128 .\48BITLBA.INF"
3.. Locate the Sysprep\I386 folder in the Sysprep image, and then create a
$OEM$ subfolder in this folder.
4.. Copy the 48bitlba.inf and Cmdlines.txt files into the
Sysprep\I386\$OEM$ folder.
5.. In your Sysprep.inf file, add a key named InstallFilesPath to the
[Unattended] section. This key must have the following value:
InstallFilesPath = "C:\sysprep\i386"
To add the preceding settings to the Images folder, which had been created
with the Riprep.exe program:
1.. On the remote installation server that contains the Riprep image,
create a Sysprep\I386\$OEM$ folder in the following folder:
RemoteInstall\Setup\Language\Images\Riprep_dir_name\I386\Mirror1\UserData
NOTE: The word "Language" in the preceding path reads "English" for the
English language, and "Riprep_dir_name" is the unique name that you selected
for the Riprep image.
2.. Copy the 48bitlba.inf and Cmdlines.txt files into the $OEM$ folder.
3.. Modify the Riprep.sif file in the
RemoteInstall\Setup\Language\Images\Riprep_dir_name\I386\Templates\Riprep.si
f folder (and any other template files for this Riprep image that you may
have created), and then add the OemPreinstall and InstallFilesPath values so
that they are set up as:
[Unattended]
OemPreinstall = "Yes"
InstallFilesPath = "C:\sysprep\i386"
4.. Close, and then save the file.
OEMs have the ability to turn this support on by means of the Microsoft
Windows OEM Preinstallation Kit.
For more information, refer to the OEM Preinstallation Kit or the following
Microsoft Web site:
http://support.microsoft.com/default.aspx?scid=http://www.microsoft.com/oem
Last Reviewed: 9/9/2002
Keywords: kbAppCompatibility kbenv kbhowto kbWinXPsp1fix KB303013
