Dell XPS studio problem 4 beeps

I've been having trouble with my XPS studio desktop. It's probably 5 or 6 years old now, but it's only recently giving me problems.

I believe it's the video card, but I can't be sure.

When I'm using it, every once in a while it freezes (sometimes it happens once every couple days, sometimes i'm a full day of freezing). It  freezes, screen goes black/monitor enters power saver, a fan gets loud, it beeps 4 times, and the power light begins to flash amber.

I recently reformatted and installed windows 7 (it came with vista). I updated the video card drivers, and it still occurs.

My video card is an ATI Radeon HD4800 series 2gb.