A. 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 a name of 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.