ATAPI / IDE drive sizes have gone up explosively in the last few years, with 100 and 200 GB drives now available as consumer-level products instead of exotic specialty items. Because of this dramatic upswing in drive sizes, versions of Windows 2000 before Service Pack 3 seem crippled, being able to see only a maximum IDE disk size of 137 GB.

To work around this problem, Service Pack 3 contains a modification to Windows referred to as 48-bit logical block addressing (or LBA). 48-bit LBA allows Windows 2000 to create and modify partitions and drives larger than 137 GB, but it requires three things: Service Pack 3, an IDE drive of that size or bigger, and a system with a BIOS that can recognize a disk greater then 137 GB. All three of these things must be present.

The third part of the equation—the BIOS—may be the biggest problem of the group, as some older systems may not have had their BIOSes updated to handle a drive of that size. If the manufacturer of the BIOS for the computer in question comes up negative, one possible solution is to buy a controller card and use that in lieu of the system's own controller. Some hard drives (such as Western Digital's Limited Edition drives, 160 GB and larger) come with a disk controller as part of the package, along with detailed instructions.

Installations of Windows 2000 that come with Service Pack 3 integrated have 48-bit LBA enabled. Any installation of Windows 2000 that shipped without Service

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Pack 3—i.e., that was patched afterwards with SP3—will need to have 48-bit LBA enabled manually. To do this, open the Registry and navigate to HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesAtapiParameters. Add a new DWORD value named EnableBigLba and set it to 1, then reboot.

If the drive was formatted on a system where 48-bit LBA was not enabled, an unallocated space beyond the 137GB barrier will appear after enabling 48-bit LBA. A new partition can be created there, or you can also use a partition-editing tool to expand any existing partitions into the unallocated space.

Serdar Yegulalp is the editor of the Windows 2000 Power Users Newsletter. Check out his Windows 2000 blog at for his latest advice and musings on the world of Windows network administrators – please share your thoughts as well!

This was first published in April 2003

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