Does anyone know of a good hardware diagnostic tool?

About 2-3 times a day, I get Windows system error messages related to my video driver (ATI driver for a Toshiba laptop). Windows resizes the resolution down to 640x480, 4 bit color, and I have to reboot. When I reboot, I get the blue screen of death, and so I power down for a minute or so and then reboot. This started a few weeks ago. I can't detect any pattern to this.

I don't know if the adapter is bad, or if I have a driver issue. The laptop is 7 months old. I pulled down the latest ATI driver, but it didn't make a difference. I'm doing searches on Toshiba's site, but wanted to ask if anyone knows of a comprehensive hardware diagnostic tool.

TIA,
Kevin