I would see if they are able to get the computer to run a system restore to a point before it was "fixed". You could also see if you can walk them through running an SFC scan in safemode with command prompt.
If not, Windows 8 and 10 both have refresh options that might get it back up and running without deleting the customer data. It just means any programs will need to be reinstalled (not ideal, but it's better than a fresh install and losing everything).
Windows 7...might be out of luck, I can't think of anything else you could try without having access to the computer.
Fingers crossed that helps!