Did you do an upgrade install of XP rather then reformat the drive and a new OS installation ?!?
I've seen weird things like this occur when doing upgrades rather then a new installation.
The only thing you should try is to get the very latest chipset drivers for your motherboard, not from the manufacturer of the motherboard but from the chipset vendor directly. If you have an Intel chipset motherboard then go to intel.com and d/l the latest INF drivers. If you have a Via chipset board then get them from viaarena.com.
See what happens after this driver update and let us know
