DISCLAIMER:
This piece of information is largely based on information from Microsoft, but neither i or Microsoft are responsible for any damages that may occur from using this piece of information.

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

The information in this article applies to:

Microsoft Windows 2000 Server SP1
Microsoft Windows 2000 Server SP2
Microsoft Windows 2000 Advanced Server SP1
Microsoft Windows 2000 Advanced Server SP2
Microsoft Windows 2000 Professional SP1
Microsoft Windows 2000 Professional SP2
Microsoft Windows XP Tablet PC Edition
Microsoft Windows XP Media Center Edition
Microsoft Windows XP Home Edition SP1
Microsoft Windows XP Professional SP1
Microsoft Windows XP 64-Bit Edition Version 2002 SP1

This article was previously published under Q305098

SYMPTOMS

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

Even if you get Windows to recognize the large drive, once you've written more than 128 Gb data on it, you will start getting corrupted files and at some point you might even get an entire corrupted disk.

RESOLUTION

To resolve this problem, run this and obtain the latest service pack for Windows 2000 or XP. For additional information, click the following article number to view the article in the knowledge base:

260910 How to Obtain the Latest Windows Service Pack

Manual installation and additional notes:

The English-language version of this fix should have the following file attributes or later:

   Date        Time      Version       Size     File name
   --------------------------------------------------------
   10/19/2001  01:42 PM  5.0.2195.4529  86,768  Atapi.sys
   04/19/2002  05:43 PM                214,938  Update.inf

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 128 gigabytes (or appx. 137 Gb if you use the IEC-notation which the harddrive manufaturers use.)
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:

Start Registry Editor (Regedt32.exe).
Locate and then click the following key in the registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Atapi\Parameters
On the Edit menu, click Add Value, and then add the following registry value:
Value name: EnableBigLba
Data type: REG_DWORD
Value data: 0x1
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 (128 Gb) 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 (128 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 128 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 128 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 128 Gb, only the first 128 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 128 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 128 Gb, the hard disk continues to function as a standard hard disk with an addressable limit of 128 Gb.
The operating system must be installed on the first partition that is less than or equal to 128 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 128 Gb.

STATUS

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.

LINKS

Tips on Windows NT 4.0 and some alternative work-arounds. (Microsoft did not release a similar little fix for Windows NT4 - i wonder if they're using this as a way to force people into buying Windows 2000 or XP?)