Check Event Viewer for errors (Custom Views...Administrative events)
Event ID 41's will tell you when the system shutdown (unexplained shutdowns)
If a bugcheck doesn't accompany it, it means that a dump file wasn't captured
Most often this is a hardware failure event (I first look for temp problems at this point)
CAVEAT: If a bugcheck accompanies it - that doesn't mean that a dump file was captured.
Analysis of this depends on when the error occurs (and the absence of a dump file).
- If early in startup or late in shutdown it's hit or miss (either hardware or dump file recording mechanisms (which includes early loading drivers).
- If solidly in Windows - then it's either a problem with the dump file recording mechanisms (
BSOD Crash Dump Generation ) or it's hardware
It's either troubleshoot 8.1 or start over and see if 8 behaves normally.
There is no 8.1 upgrade media - although you can use the 8.1 disk (from MSDN/TechNet) - but you'll need a product key for 8.1 (the 8 product key won't work).
Refresh is like the old XP repair install - but enough has changed in the OS that it just doesn't work the same. At work we rarely even bother with it - it just doesn't do the job and it's removing stuff that our customers wanted to keep.
Finally, I'm losing faith in the ability of the "Reset" to function as a wipe and reinstall. We've had a couple of problems at work that have been solved by a wipe and reinstall when a "Reset" didn't work (this is over all of our Win8 and Win8.1 installs)