Install ASUSProbe off of your motherboard CD and watch your temps. Also, make sure all of your drivers are up to date. This includes getting .NET framework 1.1 (I think) from the Windows Update site.
If you feel up to it, backup your computer, format and have a fresh install, and make sure you re-install all your drivers and stuff, and if the problem persists - see your doctor, sorry bad joke.... If the problem persists, its hardware, if it doesnt its a software prob.