Likewise I have this issue, a hard reset like the power plug just got pulled.
Had no issues of this kind on XP (still installed), running Windows 7 Professional 64-bit.
Specs are:
Core 2 Duo E8400 3.0
Memory 4GB DDR2
ATI 4850
main drive is a 640GB split in 3 (7, XP & a media drive) & a second 1TB drive.
Here's what I get in Event Viewer:
Error 16/11/2009 2:38:24 p.m. EventLog 6008 None
The previous system shutdown at 2:36:49 p.m. on 16/11/2009 was unexpected.
Critical 16/11/2009 2:38:16 p.m. Kernel-Power 41 (63)
The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly.
Error 16/11/2009 2:38:26 p.m. Eventlog 1101 Event processing
Audit events have been dropped by the transport. 0
There are no errors or anything leading up to the failure, so nothing logs as broken that I can see in Event Viewer.
I thought it might be my PSU failing, but this hasn't happened in XP, and has only ever happened once while playing games, so it's not occuring when something taxing occurs. The last few occured when listening to music, browsing with firefox, and while starting Windows.
Looking back, this has happened before, then been quiet for a few weeks, and then there's been three more in the past day.
After these reboots occur I can get points where 7 just freezes for 30 seconds or so, which is quite irritating when browsing the web, and clicking to change tab pauses the whole system (mouse still moves).
Any advice on where to start would be helpful, as chkdsk comes up clean, as did verifying windows' file integrity. I've also updated my video
driver to the latest just in case, and windows update says everything is up to date too.
Thanks.