Problem With Freezing

Ok back in the day.. We are talking about 2004 here. I had a very similar problem. Strange freezing, artifacts popping in and out when gaming and then strange colors and the computer froze. Thought it was my GPU, went to the store and they tested it. Said everything was working fine. I went with it home and nothing had changed. After looking for a similar problem I found out it could be my PSU (was not powerfull enough). Bought new and everything worked like a charm. But that said. It was long time ago. So can you test your card in another computer or tell us what type, and how powerful is your PSU?