They both went about 12 hours apart from each other. Battery pull seems to have worked for System #2. When it came back up it said something about being unable to recover from hibernation. It looks like the hardware is fine but I may need to reinstall the OS as it's unable to launch Win7 now. I'll be disabling hibernate in the future.
Someone else on the forum was having a similar issue caused by sleep mode:
Sleep mode killed my PC?
System #1 is not having any luck. Could be legit hardware failure. I did get a BSOD just before getting a few crash-boots, just before total failure. Maybe just bad coincidence that the problems occurred so close together in time. I'll keep messing with it for a bit. If anyone else has any other suggestions, please post.