First you need a consistent way to repro the BSOD. Perhaps by running a benchmark or memory stress test.
Once that happens, you can start trying to figure out what the culprit is.
If your memory is in multiple DIMMS, you should probably try one stick at a time to rule out a bad memory stick. If not, assuming you have spare parts, try a different memory DIMM. Always make sure there is a DIMM in mem slot 0 (the one nearest to the CPU socket)
After that move on to a different video card, cpu, hard drive, mobo... (If memory is not it, it will get difficult to sort out)
In my experience, when the BSOD is all over the place, it's usually memory gone bad. However, I've never seen a memory stick turn bad when left alone. I've gotten bad memory but have never had good memory go bad.