My Gut Reaction here is a multimedia driver error, but let's rule out hardware first.
Assuming you have a CD burner, download the ISO image for the Ultimate Boot CD at
http://www.ultimatebootcd.com/.Burn the disc. Boot from the disc.
Run the Memory Tester first, at least overnight. This should rule out bad memory.
Run the CPU tester next. This should rule out the CPU for errors (but not heat - keep reading.)
Run the Hard Disk Checker next. There are utilities for each of the major vendors' hard drives on the disc. Run the one that matches your vendor. You're looking for surface errors, hardware controller errors, or any S.M.A.R.T. errors. Do the "quick tests" first, and then the "detailed tests" next. The latter may take an hour or two. This should rule out the hard drive.
Next, reboot into Windows. Download and install and RUN CPUBurn-In, at
http://users.bigpond.net.au/cpuburn/.Let it run for a few minutes at first, and then longer and longer, until you run it all night. This will REALLY HEAT UP your CPU like nothing else. If your PC runs all night without rebooting or sounding a heat alarm, we can rule out CPU overheating problems.
If it passes all these tests, then I think we should start looking at DirectX, video drivers, and sound card drivers. Note that the tests I've mentioned thus far don't really touch multimedia things, but only the base hardware, which should rule that out.
Finally, check the Windows Logs for errors - do you see any?
Get back to us with the results of your tests.
-Llama
