Odd Blue Screens and Computer Behavior

[Pisces 2000]

Hello all, recently I was contacted by one of my old High School friends, who just got into PC gaming, but is having peculiar issues with his PC. About 2 weeks ago, the computer began to Bluescreen with the UNEXPECTED_STORE_EXCEPTION error, after that, the PC sometimes will turn off and restart all on its own without any blue screens, and today, it blue screened with the CRITICAL_PROCESS_DIED error. Simply put, is this more or less probably a Hardware or Software/Windows error? We've done the sfc /scannow command, ran disk error checker, deep and full scanned for viruses; at this point it's either buy new replacement hardware or reset windows, or even better, install Ubuntu. Just curious what you guys think.