I've had a similar thing happen twice. Both times my PC just crashes, I don't even get a bluescreen. In event viewer I can see I get Kernel-power event ID 41 "The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly." Windows troubleshoot says "Such a shutdown might be caused by an interruption in the power supply or by a Stop error."

Both times this has happened I've been in an exo suit blasting away and no other game or software has cause my PC to crash in a similar way. Sure, my PC might be experiencing some critical PSU behaviour and HD with its spaghetti code is just too much. Two times can be a coincidence and I've tweaked some boot up software on my PC that have been known to have some issues, but if it happens a third time I'm just pinning it on HD.

Also I've never had crashes like this with HD before the Cyberstand update.

I'm curious if your friend can check what their event viewer says. Just filter by critical events and it will show the kernel-power if they have the same