I found that to get more than 128GB of disk available on Windows 2000 SP3 (not sure about XP) you have to make a registry change to enable access to the full disk. This is due to a limit in Windows 2000 and its default ATA disk support.
Save the text between the lines below into a file called BigDisk.reg, double-click the file and reboot. You should now be able to access the whole disk. You should also check that your BIOS supports large disks, and look at updating your BIOS if not.
To save you the effort, I’ve also created the file for you – BigDisk.reg