you could try uninstalling the service pack and doing this (from the article i referenced above):
For the original release of Windows XP Home Edition or Windows XP Professional, 48-bit LBA could be enabled for testing purposes by setting a registry value, named EnableBigLba, to 1 in the following registry key:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Atapi\Parameters\
Warning Data corruption can occur you use this registry value to enable 48-bit LBA support in the original release of Windows XP Home Edition or Windows XP Professional, or if previous versions of Windows that do not support 48-bit LBA out of the box (for example, Windows 2000 or earlier) are installed on a disk partition that was previously created by a 48-bit aware operating system such as Windows XP SP1 that is larger or spans the current addressable limit of 137 GB.
they even say no guaruntees....but from what i hear about sp1, it might we worth a try. personally i think xp is a peice of garbage, had it on my computer for about 3 days before i went back to win2000pro.