Bad AGP Card???

Sounds like it could be overheating. First check that the fan spins, and second use a can of spray air to blow all the dust out of the heatsink fan. jUst be careful to keep the fan from spinning so the air duster doesn't overrev or kill the fan.

Very often one those two are the culprit. You wouldn't believe the dust buildup on a ti4200 I worked on today. I am amzed the fan could spin. If neither of these works, then try look into case air flow. Remove the side panel and blow a small house fan in at the video card. if it games fine then, you know it's an overheating problem.

If you do consider a new card, you can get a brand new AIW X800XT AGP for $179 on ATI's website. That's a killer performer in comparison to your 9800 pro with better AIW features even. If AIW features mean nothing to you, the 7800GS is even quicker, just overpriced IMO.

First try the 3 steps I gave to determine if it is overheating.

If it is, then you could remove and remount the heatsink with Arctic Silver 5, and/or mount an 80mm case fan blowing up toward the card. Buying an aftermarket cooler that fit's AIW cards is a bit tricky, so best to increase case air flow and make sure the card gets some direct cooler air. If you have a dremel, you can pop a hole in the side of the case and add a case fan and homemade ductwork that would provide cool air aimed drectly at the card. You could also just underclock the video card a bit and see if that helps. But again, first make sure the fan is spinning, the heatsink fan is clean of dust, and that a house fan aimed into the open case makes things work perfectly. If a house fan won't keep it cool enough, no internal air cooling is going to help.