Whenever I'm playing newer games on my system, after a few hours (or less if I switch between games), the graphics will start getting increasingly choppier until I reboot my computer, which seems to fix it, giving me another few hours of smooth graphics. Is this something that could be caused by memory or heating? I've got 2 GB of RAM and a Geforce EN 8600GT card. I'm not sure how many fans I've got, whichever amount Acer computers typically ship with, plus one extra recently added. Thanks in advance for any advice.