Speedy 3D have just kicked up a new article about finding the source of computer crashes, and general instability with one's computer. It's a great read as many of us have this problem. Here's a clip:
There are two main sources of instability, hardware and software. Hardware instability comes from overheating, failing, or incompatible components. Software instability comes from unstable programs, bad drivers, or software conflicts. There are several quick ways to narrow down the possibility between a hardware or software problem.