Troubleshooting Device Driver Issues

I'm having an issue where my computer occasionally hangs (~once a day, more or less). There's always pattern of red pixels that appears in the top-left corner of the screen when this happens, and it's often accompanied by the audio getting caught in a short loop.

I think one of the drivers is stomping on the memory of other drivers. I had my networking go out shortly before the crash once; everything was fine (connection, settings, etc.) but networking just stopped working, couldn't even ping the router. I was trying to figure out what happened, and The Hang occurred. I rebooted and networking was back.

I've updated my sound and video drivers. Not sure what else to do. How does one go about troubleshooting an issue like this?

The videocard is an GeForce 9800 GT. Given how many people use Nvidia cards, I have a hard time mistrusting that driver.

I'm using the onboard sound (Realtek, on Biostar TP43D2-A7) and I've seen some complains about that driver, but I honestly don't know how to narrow this down.

Any help would be appreciated.