[[X]Chipmunk™]

What Windows version he have ?
Is his Windows Genuine ?

Tell him to check his CPU usage . Maybe his PC shut down to prevent a damage to his windows system .
This can be cause of virus and unnecessary things may he have .

Quote:

This is a virus activity which prevents to use command prompt on the infected machine, this virus is called PC-OFF.bat trojan which turns off or shutdown your computer when ever you try to use command prompt by any means.

Maybe this will help:

http://www.troublefixers.com/compute...ommand-prompt/

I hope this problem can be resolved !