If you've got lots of free HD space and a DVD drive, you can do what I've been doing to stress the CPU/Memory/HD pretty good...
I ripped one of my DVD's onto my HD, both a short 10-minute section, and the full movie. I then encode them into DivX (MPEG 4) format. The smaller file takes about 20 mins and is a quick test of whatever speed I decide to run. If it passes that I let it work on the whole movie, which is definatly an overnight task.
And no..., I won't send anyone copies of the movie. I delete the encoded files when I'm done, I just do it to test stability.
Rob.