I would post you the link but it`s a german site:
This is caused by faulty/wrong driver
Which means it could come from everywhere.
Did he install any new drivers?
Or could you remove the g.card and test the PC with an other one?
Of course you checked that he had connected all cables from the PSU in the right place.
Found some in english:
Typically due to a bad driver, or faulty or incompatible hardware or software. Use the General Troubleshooting of STOP Messages checklist above. Technically, this error condition means that a kernel-mode process or driver tried to access a memory location to which it did not have permission, or at a kernel Interrupt ReQuest Level (IRQL) that was too high. (A kernel-mode process can access only other processes that have an IRQL lower than, or equal to, its own.)
On the MS webpage they say it could even be causeb by antivirus software! (LOL?)
Edit: We got two votes for a driver issue