Yes, a bad power supply or a loose electrical cord connection to the power supply, could cause a PC to crash. I don't know if this will work to recover Vista from the windows.old folder (it works for XP), but it might be worth a try:
http://support.microsoft.com/kb/933168.
As for the activation, you get 30 days and can get up to 120 days by setting back the timer; it might get you enough time to solve your current issue: When you hit your 30-day mark > Right-click the command prompt and select run as administrator > Type "slmgr -rearm" and hit enter. This will give you another 30-days.