Just to add to the general conversation, since I think it has merit: it's funny how relevant all those "do a proper uninstall" threads we have since the dawn of time really are... i've had hard resets lately on one of my PCs whenever I played games. For no particular reason. Nothing in the Windows 7 event viewer, no sign of any error, nothing. I had 10.4 still on. So I upgrade to 10.6, same thing. Yesterday, I dig up DriverCleaner (excellent program, go here to get it, well worth the money: http://www.drivercleaner.net/)
, uninstalled everything via the Catalyst Installer, immediately followed by a DC pass cleaning up everything ATI-related, and then, after I rebooted, installed 10.7. Fixed it right up.
Do a proper uninstall once in a while. Does wonders