Have you tried pulling the card out of the slot, giving it a good dust off via compressed air can and putting it back in? I'm no hardware expert or anything, just a thought.
Was new when I bought it, and it was pretty cheap (£70/~$140)
Haven't had any problems other than the occasional screenspike when it needs updating. Other than that they tended to go away when I updated the drivers. This hasn't.
P.S. Will try cleaning it today. Have some PC hoover attachments or whatever.
EDIT: This is what I mean by "weird pixel patterns:"
Took the computer apart and got the kit out and cleaned every bit of it, but nothing.
I think I'll just save my money up and buy a new computer. I mean, this is a few years old, and pretty crap.
The only annoying thing is is that James still hasn't made his ****ing mind up about selling his old one. So I have to wait about a week to see if he'll let me buy it instead (because he's a self-centred greedy neurotic bastard that has no idea what things are worth).