Source: Kernel-Power
Type: Critical
Description:
The last sleep transition was unsuccessful. This error could be caused if the system stopped responding failed or lost power during the sleep transition.
Comments and links for event id 41 from source Kernel-Power
Source: Kernel-Power
Type: Critical
Description:
The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding crashed or lost power unexpectedly.
http://www.eventid.net/display.asp?eventid=41&source=
Second one applies to you.
Well, if you want to rule out a corrupted Windows install, reinstalling that would be next. If it still persists, it's probably a hardware issue. If you have any unallocated HDD space you can simply try installing a second instance of Windows. You can simply delete the partition if it doesn't help.