Super PI really works. If your computer locks up, I say you have something wrong.
I once bought a slightly used state of the art Pentium from a con man on Ebay. My computer had occasional hard to diagnose problems.
Super Pi came to my rescue. As long as I calculated PI to less than 4 Megs, everything was okay. If I tried 4 megs or greater, bad things would happen. When running XP, the OS would crash. If I was running Win2k, the OS didn't crash, but SuperPi would find an internal error and stop calculating.
There's nothing wrong with Super Pi either. It runs fine on my other machines, and it runs fine on that machine since I replaced the CPU.
Apparently the con man was getting these Pentiums from Intel's dumpster.