i suggest running a burn in wizard such as sisoft's sandra - its good enough (you don't need to run a loop all night long its pointless). also 3dmark will work, just grab the demo version and run around 10 loops, you'll know you're stable if it passes them all. otherwise, you can always run sandra and seti or something of the likes to test stability as well.
<b>and now for something completely different</b>
...<b><A HREF="http://bytethiscomputers.sytes.net/site/specs.html" target="_new">system specs</A></b>