stress test laptop to see if will crash - tips?

I sometimes get reports from my students that the laptops I lend them have started not working.  When I get them back I boot them and they seem to be OK.

I have gone and run the classic unix "crashme" program to stress them with load and threads and memory access, but they go along nicely.

I wonder if anyone has a favorite program to stress the system, disk, display, memory, CPU, ...  Display seems important: sometimes the problems I've seen had to do with the video drivers trying to use advanced hardware features that are not well supported.