Windows 7: [help] Windows 7 artifacts, bad sound and no safe mode

hey there,
well, i have a new problem and i cant seem to find anything anywhere about this specific problem, there are many others who have similar ones but mine seems to have added extras.
for example, on my windows 7 Professional 64-bit desktop computer, i can start it up fine and it will run a web browser and steam/msn for hours, but as soon as i try to start a game it will either crash or get artifacts. after i close the game sometimes it wont be right until i restart. it is not consistant at all. i also occasionally get little bugs in the display, i wouldst really describe them as artifacts because they only cover up specific parts, for example, there are black squares over some bits of writing in task manager etc. most of you are probably thinking that it is overheating at this stage from these symptoms, but i checked that and no components reach over 40Celcius at idle. i did a stress test and from memory it stopped at under 60Celcius. also, when i did the stress test i got NO artifacts...

another issue i have is that sometimes after my computer has been running for a while with me using it normally (google-ing how to fix this ) my display will restart. as in the screen will turn off for a few seconds and then start again, i believe that it is my video drivers restarting becuse after it happened i opened up task manager and there was a huge CPU spike to 100% right after it happened, which i assume is the driver starting back up. it will do this several times over a minute or 2 with freezing as well (the kind where i cant move the mouse), until it finally gives up and the screen just disconnects (what i mean is that it is the same as when i physically unplug the screen from the computer.).
along with this problem also comes another, just before this happens, sometimes my sound will stuff up, not fully, but it will just go all crackly and switch configuration (i have surround sound, it is set up so that music only plays through the center speaker. it will switch between the center speaker and all 5 every few seconds).

another problem:
i also have the one where i cant start in safe mode because of that one stupid CLASSPNP.SYS file, there are plenty of threads on it on this website, and i have a few ideas on how to fix this specific problem. but i was wondering whether it was related to my problems.
EDIT: i have now fixed this problem by replacing CLASSPNP.SYS with one off my brothers computer and i just got into safe mode. going now to see if it has fixed my other problems
UPDATE: appparently not.

what i have tried:
1. i have tried changing the voltages in my BIOS in case the GPU etc weren't getting enough power.

2. i tried scanning the whole computer for viruses.



3. i tried removing a LOT of stuff from startup

4. i tried closing a LOT of un-needed processes.

5. i tried using 'ccleaner' and scanning for registry problems.

6. i tried 'turning it off and on again'

7. i tried asking other people.

8. i tried using a big fan and facing it into the computer

9. and now i am trying asking MORE people.

UPDATE: after much digging, we have discovered that there is a lot of data corruption going on! it appears as though it is occurring only after using the file in question, for example, i opened WoW.exe and it crashed, i restarted, and now it is 0Kb. same with all my Halo savegames after i tried playing that. Doing a FULL check disk on the drive now.


MY COMPUTER SPECS.
Processor: Intel(R) Core(TM)2 Duo CPU E7600 @ 3.06GHz (2 CPUs), ~3.1GHz
Memory: 4096MB RAM
Hard Drive: 1 TB Total
Video Card: NVIDIA GeForce 9800 GT
Monitor: teeny
Sound Card: realtek high def audio
Speakers/Headphones: logitech z5500
Keyboard: APLLE
Mouse: generic logitech
Mouse Surface: TP-LINK - the reliable choice
Operating System: Windows 7 Professional 64-bit
Motherboard: gigabyte ep45 - ud3l
Computer Case: Homebrand

did i mention that i needed help fixing it?