This is taken from this article, rithym. Hope it helps a little. click here
"XP Service Pack 1 (SP1) adds support for 48-bit Logical Block Addressing (LBA) for ATAPI drives, which lets the OS access hard disks larger than 137GB (the current limit). For this change to work, you must have
- a 48-bit LBA-compatible BIOS
- a hard disk with a capacity greater than 137GB
- XP SP1
To enable 48-bit support, perform the following steps:
1. Start a registry editor (e.g., regedit.exe).
2. Navigate to the
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\atapi\Parameters registry subkey.
3. From the Edit menu, select New, DWORD Value.
4. Enter the name EnableBigLba, then press Enter.
5. Double-click the new value, set it to 1, then click OK.
6. Reboot the machine for the changes to take effect."