Ah yes...XP is a big ram hog indeed. That's the problem. There's no hidden problem really. You just simply do not have enough ram to run smoothly. Buy some ram.

I like
www.pcinfinity.net for my parts. No shipping at all. You pay a small insurance fee (like a dollar something) when you order, but that's it. Getting a whole pc shipped for a dollar or two is a nice deal.