I think I mentioned this already but I use the Cerberus test suite
http://sourceforge.net/projects/va-ctcs/
Haven't had to use it in a while but works quite well, a lot of big OEMs use it as well for their burn in tests. For me it found problems much faster than memtest86. Apparently it was developed by VA Linux(If your familiar with that name)
Been meaning to setup a pxe linux boot environment with this in there so I can run it without the full blown OS on there, but haven't had a chance yet.
nate
Thanx nate, I'll check it out :)