How old is "a few years"? 3? 5? More?
If it's 3 years or newer, go ahead and focus on the MB which it sounds like it could be. If it's older than that, I'd just do a new build with modern parts.
I am too lazy to look, but I would say 2 years? Its a 6th gen CUP, and a 1060 video card so not real old stuff.
I ordered a replacement power supply (I bought the one I used yesterday as a test with plans to hold onto it for future troubleshooting), and a new MSI Z370 MB. I hate to throw parts at it, but I am trying to have this fixed for her this weekend. I think its the MB, so I figured I would get my hands on one if I need it. My plan today is to take the MB out of the case, and bench test it with the new PSU that I got yesterday. I can verify that nothing in the case is shorting the board, and I can go through components one by one to validate them. Ill have a fresh MB and PSU on stand by. I can pull memory from my systems easy enough to check if need be. If its a CPU, well we can cross that bridge when we get there.
Just trying to fix this for her without building her a new computer. Sure would have been nice if it was just the PSU
Sean