It can be hard to troubleshoot, depending on cause and tech level. From your brief explanation you have some immediate suspects that jump out. Are you overclocking at all? It sounds like memory issues, I'd start by downloading Memtest from the stick in the CPU section. If it doesn't pass, try manually setting your timings and voltages (I start with mfr recommendations, though if you want to tweak performance you might try a more systematic approach to optimizing timings). If you still can't pass try 1 stick at a time to see if either is bad, and verify through the memory mfr that your memory is compatible with your MoBo. If it passes Memtest but you still have the issues, then it can get complicated. Start with going into your event viewer to see if any specific error is occurring that might be the cause of your problems. Any error codes should be run through a Google search to narrow the cause. Also watch your temperatures to see if they're going to high and your voltages (Asus Probe) to verify they're within tolerance and not fluctuating excessively. Turn off the reboot on error option in Windows (I'm assuming XP) and write down/Google any error codes you generate on reboot. Run a Scan Disk on your HDD to make sure that you haven't generated any errors on the drive, and I like to turn off the auto restore feature in Windows if a system is demonstrating instabilities as it's a common problem to generate errors in the restore points. Make sure your hardware drivers are up-to-date, esp video. You might try Googling to see what drivers others are running with that particular video card. If you haven't turned anything up after that, then it's time to look at the CPU as a possible culprit. Again in the CPU forum download one f the strss tests (I'm used to Prime95) and see how your temperatures/stability runs.
