I recently had to do some work with my wife's machine--and tested quite a few things before finding the culprit. You might get some ideas from my post:
viewtopic.php?f=2&t=73751
In my primary machine, though, several months ago I was getting some errors similar to the ones you reported. The culprit there turned out to be a bad hard drive, and I didn't actually succeed in identifying the source of my blue-screen crashes until the drive actually failed, unfortunately. In 25 years it's about the third hard drive, out of dozens I've owned, that actually failed before I had the chance to voluntarily retire it. Good luck!