4870 Artifacts

[Astronomica]

Just in this past week my 4870 started spitting out artifacts while gaming and has been progressively getting worse. I was wondering what the best course of action would be in attempting to fix this problem. Some time back the fan broke on this thing and i replaced the cooler with a Accelero a few months ago. Since it's technically been modified/damaged HiS won't honor the warranty on it, so it's going to become an expensive paperweight. All the temps on the board are well in the safe zone, and I've checked the 12v with a multimeter and it doesn't appear to be a power issue either.

So short of baking it in the oven or using it to hold papers, anyone got any ideas on how to go about fixing this?

Picture for reference.