Windows suddenly says "no audio devices" while i'm using it.

[Camaro]

Hello, everyone!

this time, i'm having an awkward problem - i tried everything that came to my mind for about 2 weeeks already and i didn't get it fixed yet.

It all started when i played around with the sound settings of my onboard VIA HD audio chipset: The HD Audio deck program froze. And after a restart, it continuously popped up, because it kept telling me i just connected my microphone (as if i plugged it in and pulled it out again the whole time).

I deinstalled and deactivated the device, then reinstalled it with the proper drivers from the VIA homepage.
- everything worked fine again!

... until a week (or so) ago, and since then i have the following problem:

After a random time of using my computer, my explorer will flicker shortly; either looking normal afterwards OR chaning my taskbar to one that is grey, like windows 98 or 95.

From then on, if i start for example LFS or rFactor, i will hear no sound.
If i start winamp, it will tell me i have no proper sound device (error code 88780078). So then i go to System -> Sounds and Audio Devices, which will also tell me i have no sound device.
Weird Fact: If i have skype running while the error takes place, the conversation will not be affected at all.
Also, whhen i click on winamp, i can still hear the "Bing"-like error sound of windows.
If i go on youtube i can then still watch and hear videos normally.

Trying to avoid this problem, i deactivated and deinstalled the VIA chipset in the hardware-screen, and also inside the BIOS (it's called AZALIA AUDIO there?!).
Then i dug out my Trust External Soundcard (prduct id = 14134-02), which i bough a few years ago, because my old PC's VIO Onboard was also broken. I installed that one with the proper drivers.

Then i noticed that windows finds an "audio port on high definition" (or similar to that), no matter if my external sound card is connected or not (onboard sound is still deactivated in bios!). - i choose to install the VIA drivers for it.

The error, that after a while, windows will deny to have any audio device is installed still exists; it will be fixed for a time though if i just re-install a driver for my sound card (either "VIA" or "Trust external").

I can add Screenshots of any sort if needed, though they will be in german.
I really hope anyone knows a help to this problem, i am at the end of my knowledge, and nerves! i dont want to have to format my HDD and start from scratch
(maybe theres something in the registry i can do?)