Plz humour another bottleneck question :)

It is tough to say for sure, though you should be doing better than 20-30fps min even with that older processor. What is the Resolution that you are running? Are your temps stable on the CPU? I just installed a much lesser video card in a computer with very similar specs (same CPU and amount/speed of RAM), and he was playing wow and CoD4 with great fluidity afterwards.

Since you didn't mention your OS or if you did a clean install of it, to help diagnose the issue, I would suggest doing so. A clean install on a formatted HDD, that is properly updated with the newest drivers for your card downloaded and installed is the first thing I do when having issues of the sort.

Now that is a coincidence: the computer I put another card into last weekend had an 8500gt that died (fan died and the card burned itself out), but was running vista. I installed a 4670, with a 380w coolmax PSU, 4200+ not-oc, and 2gb 800mhz ram. It ran like a champ at higher resolutions than what you are running.

Definitely resintall windows, update, and drivers. Clean out your case with compressed air. If there is any buildup under the CPU fan, remove the fan (not the heatsink) to get at what might be under there. The drop in FPS AFTER you are already running faster might be attributable to a buildup, and eventual downclock, to protect itself from overheating.

If after all that you are still being dissapointed, try return the card for exchange/refund. You should be doing better than what you are gettings.

He should still be seeing an improvement over an 8500GT, which he isnt, which means that something else is wrong. Probably a driver issue, but I have always had difficulty installing ATI cards to replace Nvidia without doing a windows re-install, due to resilient driver issues.