My friend's PC suddenly stopped displaying to the screen (no video signal), the PC turns on but it doesn't turn off when holding down the power button (the LEDs in the PC keep flashing). So I put my PSU into his PC but it didn't work (same as before) but when I put the PSU back into my PC it ruined my PC as well. No display, it turns on but I can't turn it off (same as his). I tried it with a third PSU but it still doesn't work. So somehow his PC ruined my PSU and when I put it back into my PC it ruined my PC as well? Is that even possible? I'm in total shock right now.