48-Bit LBA Support for ATAPI Disk Drives in Windows 2000

Windows 2000 Service Pack 2 (SP2) and earlier versions of Windows 2000 do not support 48-bit Logical Block Addressing (LBA) as defined in the ATA/ATAPI 6.0 specification.

To resolve this problem, obtain the latest service pack for Windows 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base: The English-language version of this fix should have the following file attributes or later:
The following conditions are necessary for the correct functioning of 48-bit LBA ATAPI support:

• A computer with a 48-bit LBA-compatible Basic Input/Output System (BIOS) installed.
• A computer with a hard disk that has a capacity of greater than 137 gigabytes (GB).
• You must enable the support in the Windows registry by adding or changing the EnableBigLba registry value to 1 in the following registry subkey:
  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\atapi\Parameters

To enable 48-bit LBA large-disk support in the registry:

1. Start Registry Editor (Regedt32.exe).
2. Locate and then 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.

NOTE: If you enable 48-bit LBA ATAPI support by editing the preceding registry key, but your system does not meet the minimum requirements, you may observe the following behaviors:

• Operating systems that do not have 48-bit LBA support enabled by default (such as Microsoft Windows 98, Microsoft Windows Millennium Edition (Me), or Windows 2000) that are installed on a partition that spans beyond the 28-bit LBA boundary (137GB) will experience data corruption or data loss.
• The installation of operating systems that do not have 48-bit LBA support enabled by default (such as Windows 98, Windows Me, or Windows 2000) on a partition that is beyond the 28-bit LBA boundary (137 GB) is unsuccessful and leaves behind a temporary installation folder.
• If you install hotfixes that enable 48-bit LBA before you install Windows 2000 Service Pack 3 (SP3), the appropriate registry key will be automatically created during the installation of SP3 to preserve the data integrity of the hard disk.
• After you enable 48-bit LBA support by adding the appropriate registry key, data corruption may occur if you remove the registry key or if you remove (uninstall) SP3 for Windows 2000.
• If you install a copy of Windows 2000 that includes SP3 (SP3 integrated) on a large hard disk that has already been preformatted by using a 48-bit LBA-enabled operating system, the ATAPI subsystem may report hard-disk space greater than that which is addressable without the 48-bit LBA support (larger than approximately 137 GB) during the text-mode portion of Setup. In this case, the hard disk's partition table information has already been created. To fix the incorrect disk information, delete the partition by using either a disk partitioning utility or by deleting and then re-creating the partition during the text-mode portion of Setup. After you create the new partition, quit Setup by pressing F3, and then restart the Windows installation process. The ATAPI subsystem now correctly shows approximately 137 GB of hard disk space.
• The EnableBigLba registry value is disabled:
  
  If you have a 48-bit compatible BIOS that can support a hard disk that has a capacity of more than 137 GB, only the first 137 GB of the hard disk is addressable. The remainder of the hard disk is not used.
• The operating system must be installed on the first partition that is smaller or equal to 137 GB when the EnableBigLba registry value is enabled but when you do not have a 48-bit LBA compatible BIOS.
  
  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 of more than 137 GB, the hard disk continues to function as a standard hard disk with an addressable limit of 137 GB.
• The operating system must be installed on the first partition that is less than or equal to 137 GB and the rest of the hard disk divided into one or more remaining partitions when the EnableBigLba registry value is enabled on a computer without a 48-bit LBA compatible BIOS that has a hard disk with a capacity of more than 137 GB.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Windows 2000 Service Pack 3.Important Although support for 48-bit LBA is included in Windows 2000 Service Pack 3 (SP3) and later, it is still necessary to create the registry change that is described in the "Resolution" section of this article.

For additional information about how to obtain a hotfix for Windows 2000 Datacenter Server, click the article number below to view the article in the Microsoft Knowledge Base: For additional information about how to install multiple hotfixes with only one reboot, click the following article number to view the article in the Microsoft Knowledge Base: For additional information about how to install Windows 2000 and Windows 2000 hotfixes at the same time, click the article number below to view the article in the Microsoft Knowledge Base: