Artifacting Constantly

I use a 9500GT 1GB and for the past 8 months or so I've seen on an off artifacting in games. I'd say in the past month it has really come to a head, shutting down WoW every 15 minutes. I've set everything to the lowest possible settings, both in game and on the card.

I have a 650watt PSU, 2GB of ram, and dual core 3.0.

I've been using HWMonitor to keep tabs on the temp, but it has yet to pass 65C, even while artifacting in game. I've run Driver Cleaner Pro and reinstalled current drivers along with reinstalling mobo drivers. I picked up FurMark and didnt have a problem whatsoever. I've also run a Memtest, and completed the first pass with no errors(I'll leave it on overnight tonight.) The artifacting isnt limited to WoW, ive had it in a few other games as well, along with a few movies.

I purchased the computer from a 3rd party site who put it together for me(Ibuypower.com). I KNOW my HD was recycled because it had folders from the previous user on it(empty ones that is). Wondering if overclocking damage from a previous user may have gone undetected. Or if the problem is somewhere completely different! I'm setting up an RMA today, but I'd like to know if there is something I'm overlooking.