This article was previously published under Q303013
This article describes the Microsoft Windows XP Service Pack 1 (SP1) 48-bit Logical Block Addressing (LBA) support for ATA Packet Interface (ATAPI) disk drives that can increase the capacity of your hard disk to more than the current 137 gigabyte (GB) limit.
Note Windows XP does not support 48-bit LBA support unless you are running Windows XP SP1. If you want to use 48-bit LBA support, you must apply Windows XP SP1 or later. Windows XP Media Center Edition and Windows XP Tablet PC Edition already include SP1.
For additional information about the latest service pack for Windows XP, click the following article number to view the article in the Microsoft Knowledge Base:
322389 How to obtain the latest Windows XP service pack
Windows XP SP1 includes 48-bit LBA support for ATAPI disk drives. With this support, you can use hard disks that are larger than the current 137 GB limit. By default, support is enabled in SP1. To determine if you are running SP1, right-click My Computer and then click Properties. On the General tab, Service Pack 1 will be listed under "System."
To determine if you have the latest ATAPI driver, verify that you have version 5.1.2600.1135 or later of the Atapi.sys file in your %systemroot%\system32\drivers folder. (Or version 5.1.2600.1152 for Windows XP 64-Bit Edition.) To do this, follow these steps:
Click Start, click Search, and then click All Files and Folders.
Type Atapi.sys, and then click Search.
If you do not find the Atapi.sys file in your %systemroot%\system32\Drivers folder, click More advanced options in Search Companion, click Search hidden files and folders, and then repeat step 2.
For additional information about how to search for hidden and system folders, click the following article number to view the article in the Microsoft Knowledge Base:
302347 How to search for hidden or system files in Windows XP
Right-click Atapi.sys in your %systemroot%\System32\Drivers folder, and then click Properties.
Note the file version on the Version tab.
If Atapi.sys is not version 5.1.2600.1135 (or version 5.1.2600.1152 for Windows XP 64-Bit Edition), obtain and install the hotfix that is described in Microsoft Knowledge Base article 331958.
For additional information about this hotfix, click the following article number to view the article in the Microsoft Knowledge Base:
331958 Hard disk may become corrupted when entering standby or hibernation or when writing a memory dump
By default, the original release version of Windows XP Home Edition and of Windows XP Professional do not have 48-bit LBA support. Your computer must meet the following requirements to use 48-bit LBA ATAPI support:
48-bit LBA-compatible BIOS.
137-GB hard disk or larger.
You must have Windows XP SP1 installed.
For the original release version of Windows XP Home Edition or of Windows XP Professional, you can enable 48-bit LBA for testing purposes. To do this, set the EnableBigLba registry value to 1 in the following registry subkey:
Warning Data corruption may occur if either of the following conditions is true:
You use this registry value to enable 48-bit LBA support in the original release version of Windows XP Home Edition or of Windows XP Professional.
You install an earlier version of Windows on a disk partition that was previously created by a 48-bit aware operating system, such as Windows XP SP1. And that disk partition is equal to or larger than the current addressable limit of 137 GB.
Note The previous registry setting is ignored in Windows XP SP1 and later. If you try to enable the 48-bit LBA ATAPI support in the original release version of Windows XP Home Edition or of Windows XP Professional by editing the previous registry setting, and you did not meet the minimum requirements, the following issues may occur:
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 rest of the hard disk is not used.
The registry value EnableBigLba is enabled, but you do not have a 48-bit LBA compatible BIOS and the capacity of the hard disk is not greater than 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 see comment than 137 GB, you have not changed the system. The hard disk continues to function as a standard hard disk.
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 see comment 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 using an unattended installation with the Microsoft System Preparation (Sysprep) tool, follow these steps:
Copy the following text into Notepad and save the text as the 48bitLba.inf file: