Hi AlleyCatty. First provide the list of the latest Event Viewer errors.
A failing / marginal power supply can cause all sorts of seemingly unrelated software and hardware errors that can't be tracked to a specific source. But you can observe the main power supply outputs and generally determine whether it is working properly or not. Install Everest Home and see if the voltages are within these good operational ranges at all times:
+3.3: 3.135V to 3.465v
+5: 4.75V to 5.25V
+12: 11.4V to 12.6V
Also look at the "Temperatures" section under "Sensor". The CPU temperature should be under 50 degrees C. While playing movies or games also keep Everest running and check it from time to time for the voltages and temperatures. Perhaps you will be able to diagnose a heat problem or a failing power supply.http://www.majorgeeks.com/download4181.html
Everest Home (Free)
I won't trust any Windows-based memory diagnostic because their are huge blocks of RAM that are in use at any one time and cannot be tested properly. Download and burn Memtest86 or Memtest86+ to a CD.
This will be a self-booting disc. Make sure your BIOS setting has the devices' boot order such that the optical drive is listed before/above the hard drive. You will need a burning program that can burn .ISO image files to a CD such as Nero, Active ISO Burner (free) or CDBurnerXP Pro (free).http://www.softpedia.com/get/CD-DVD-Tools/...SO-Burner.shtmlhttp://www.cdburnerxp.se/
A general-purpose burning program
Just load the burnt CD in your master optical drive and restart your PC. Memtest86(+) will load and run by itself. Let it run at least 3 complete passes. It should list no errors. If it does, turn off the PC, take out all but one RAM stick and re-run the diagnostic. Keep switching the RAM sticks until you find the bad one(s). To stop the test at any time unload the CD and push the power or reset button.
The problem with the drivers for the on-board sound chip seems unrelated to the crash/freeze problem. Make sure the sound chip is still enabled in the BIOS. If it is then reload its drivers. If the drivers remain missing then Uninstall the sound adapter in Hardware Manager and restart your PC. Hopefully XP will automatically reload the drivers and get the device working again.