Echo that, I'm leaning towards MoBo. General rule of thumb, if you pull a MoBo or power supply, pull them both out AND the RAM. But try the BIOS settings first.

That being said, I've seen a lot of Dell's just decide they don't like RAM any more. The RAM is usually still OK, but the glitch is on one of the controllers on the MoBo. When I did tech support in college we had them shipping us replacement parts pretty much weekly.

A NEW XP friendly computer is getting harder and harder to do unless you want to build your own. If you are going to buy one, don't do anything with any of the chains and big makers, spend a little more and find an independent who will work with you. The chains and builders is that they have deals with Meglosoft that bar them from putting XP on most machines these days. There was a special waiver for the netbooks and some other small, lower performance machines, and AFAIK, that's it.