Random PC Freezes revisited

Hi,

As the thread title suggests, My PC freezes (semi-)randomly.
Actually, I would like to refer to a previous thread with the same title as I believe it might be the exact same issue.

OK, first off some of my specs and situation overview, if I forget something, you'll be sure to point me out.

- I ran Vista 64bit and reinstalled my C: partition some months ago with Windows 7 Home Premium edition 64-bit.
- I have a Intel Core2 Q6600 2.4Ghz CPU
- On an ASUS PK5 motherboard
- With 4x 1GB Corsair DDR2 (PC2-6400) memory
- And an NVidia GeForce 8800GT graphics card

Now ever since the install of Windows 7 I get these random crashes, even when no extra software or games were installed.

I said in the beginning that the crashes were semi-random, as they do happen sometimes with no explanation at all.
But for example when I run Heroes of Migh and Magic 6, after about 5 minutes, the PC freezes. But it's not related to the game, as it happens at a different moment each time and has the same symptoms as the random freezes which occur sometimes not, sometimes once or twice a day.

The symptoms of a freeze are almost always the same:
- Everything freezes up obviously
- The screen gets scrambled with trembling pixels (you know, the little horizontal stripes in magenta color kinda)
- And the sound hangs too giving an annoying hanging record-sound.
-The only solution is pushing the reset button.

Now, what have I already tried (with no succes):
- Updated Graphics card drivers to the latest
- Tried playing with the power saving options

Before I actualy take on the Bios (which is now version 0603 and the latest is 1201) and change the voltage or timings parameters on my memory, I would like you guys to give me your professional feedback...

Thanks,
Hiapoe