Prime95 -> you use the "torture test" option in the program.
It stresses cpu & mem, so you can check to see if it's stable.
If it's not stable, it tells you it had an error in calculations.
If it's stable, it just keeps running.
Usually you can tell if something is stable within 10-20 minutes. I will let mine run a couple hours to test, when I'm finalizing something.
You can also use it as a burn-in proggy.
Search for it on google.
Very interested in the results, so definitely post them.
2100 mhz on air for $101 is a good ratio -> $.21 per mhz. :D