My PC has started randomly powering off after, at most, 10-20 minutes. Once it's "warmed up" it generally powers off after only a couple of minutes. When it powers off, it behaves as though the power was simply unplugged or there was a sudden power outage. No BSOD, etc. My only guess is that it's an issue with the power supply, because Windows sees nothing wrong with hardware (aside from reporting that it failed to boot or crashed unexpectedly).
So, a couple of questions:
1. Does this sound like a power supply issue?
2. How can I test my power supply?
As a side note, this of course happened after I started planning a PC upgrade and then decided against it. Murphy's Law, eh?