So I've got this weird series of problems I can't figure out. First my computer was randomly shutting itself down in the middle of use, which the windows event log claimed was because it was receiving a signal from the power button. Ok, fine, maybe the button is faulty, it's a pretty old case. I tried disconnecting the power button lead from the motherboard's pins and moving the reset button's lead onto the power switch pins instead, which should have totally worked, but then the computer started shutting off every time during windows' loading screen before the login screen. I switched the front panel button wires back to their previous pins on the mobo and the new shut down during windows boot problem remained so I was kind of at a loss. Then I tried disassembling the front panel and cleaning the switch guts out of dust, and also I disconnected the power supply from the new hard drive I had added a week ago and had seemed to work fine up to this point. Then for some reason the system booted fine after I did that! And the system event log shows no record of (or I don't know the right place to look for) the power losses during windows loading or the interrupted windows boots, so I have no idea what was causing that. Also the random shutdowns are still happening, like before I messed with anything.
My best guess at this point is that the power supply might be dying, as it is pretty old, and putting another hard drive on the same cord as my SSD was making it start to get erratic for some reason, even though it was fine before this random shutdown behavior started 2 days ago. Does that sound possible? Any other ideas? How should I test my PSU to see if I need to replace it?
I figure I should at least get new switches for the power and reset buttons, I think I see how to replace them if they're a standardized shape.