I'm with B about the RAM on this one. Although, I might test it out first with Memtest86 to make certain it is the RAM which is at fault.

Also, I think Sniper pegged it dead-on as far as upgrades are concerned. If you do want to upgrade, which I personally don't feel is entirely necessary for you, Snipe's more conservative recommendations will offer great performance and will be substantially easier on your pocketbook.

-AT