sounds like a hardware issue still XP may just be a little more forgiving.. I say this alot but more info is necessary How much RAM is Installed? What type? What speeds? The omly real thing i can suggest with so little info would be to shut down,de static, unplug, remove and re seat your memory a little dirt can go a long way with memory problems.I don't know how much memory your unning but if it's enough can you boot with half removed you may have a bad module.