A friend of a friend has been working on my PC to deal with a long standing problem which he said he had fixed. When my son plugged in the power lead the PSU blew up. I checked the rear and found it had been set to 115v. How could the machine have been running at that voltage during the tests he was runnning? I tried a replacement PSU but the machine is dead. I assume there has been damage to the motherboard. Is it likely to be terminal?