Sudden crashes.

[Critz]

I have a really bad problem - when I play, the music suddenly starts to loop every few seconds and after a few loops, the game crashes, along with the PC (Alt+Tab and Ctrl+Alt+Del don't work) - the screen completely freezes, the music stops and I can only reset the PC. It happens randomly in SA (and always at the beginning of S6), my brother got it few times in FW, MoF once crashed for me as well, and even Hisoutensoku did crash once. I only play Diablo 2 LoD along with Touhou lately, but it works fine. And I had my system partition (C:\) formatted once since it started to happen and it didn't help. A few months ago I changed my video card, but back then I was able to play the games just fine, so I don't think that's the reason. Also, my PC recently started to scan D:\ and E:\ partitions during system start until I reinstalled the system. The formatting was caused by turing off power from the PC when it froze, and after I turned it on, I got "Unmountable Boot Volume" message.

My hardware:
Windows XP Pro SP3
AMD Athlon XP, 1466 MHz (11 x 133) 1700+
1GB RAM
ATI Sapphire Radeon X1650 512 MB (changed from GeForce 4 MX 440 SE 64MB).
Mainboard: MSI KT4V (MS-6712)
Intergrated audio: VIA AC'97

I also scanned disks for viruses. I'm completely out of ideas. Help, please :/.

[Momiji]

Your motherboard uses the VIA KT400 northbridge chip, which is notorious for problems like this.  Things to try:

1:  Make sure your BIOS is as current as you can get it.
2:  Downclock your RAM in the BIOS, step by step until the system stabilizes.
3:  Disable "AGP Fast Writes" in the BIOS.
4:  Make sure you install the absolute latest drivers for everything in your system.
5:  Ensure that your RAM sticks are matched exactly, if you're not using a single stick.
6:  If you can stabilize your system somewhat, you can try testing your memory for errors.
7:  Check the wattage on your power supply.  It should be at least 300W, maybe even 400W or greater.
8:  Finally, make sure all your fans are turning smoothly and the heatsink(s) are clean of dust and debris.

Most importantly, don't ever ever ever put a Soundblaster card (Live! or Audigy) in your system.

Once your system's stabilized, then you can try reinstalling Windows.

[Critz]

After a few more crashes, my XP user profile got deleted and it started to boot with temporary profile. So I decided to try something radical and formatted all of my disks, only moving my most important files between partitions to not lose them. This finally worked. I don't have the most recent BIOS, since MSI Live Update gives me a blue screen and I'm not confident enough to try on my own unless as a last resort. And I believe my wattage is 400W. It doesn't matter now, but I'll keep your advice in mind for the future. Thanks a ton!

EDIT: Hisoutensoku of all games just crashed again. SA seems to be fine though. Might have to try your advice tommorow after all.

EDIT2: One C:\ format later, I went even more radical and set the FSB Clock from default 133 to 100 MHz. Finally seems to work. More testing will ensue.