Windows XP 64 bit has been an ugly duckling since it's inception, and there have been very few (hardware)drivers available for it.
If you want a 64 bit Windows OS, go for Windows 7, or Windows 8 if you want/have to. Even Vista x64 was a small drama (I've used it for 2,5 years myself
Only since the wide acceptance of Windows 7 x64, manufacturers have been supplying 64 bit drivers for it (yes, Vista x64 started it too, but to a lesser extend), but drivers are usually not back-ported to older OS versions. There's not enough market to gain.