Hmm weird.
Something seems to have happened to some settings.
FIRST PLAN OF ACTION:
Has he by any chance installed Video Drivers recently?
Its possible anyway that his monitor could be displaying a second monitors screen which would only show the desktop.
Tell him to right click the desktop and go to Properties, and go to the 'Settings tab' at the top.
From here, tell him to make sure the monitor is set to display as the first monitor by dragging the little boxes if there are two to the other side, or by simply selecting the right display from the drop down box.
-------------------------------------------------
SECOND PLAN OF ACTION:
If that doesn't work, at least you know that hasn't occured.
This should work in that case.
Ask him to right click the empty desktop first of all, and go to "Arrange Icons By", and select to "Show Desktop Icons".
If that works, nothing is neccessarily wrong.
So, now, My computer should at least display. Tell him to go into that and on the side bar should be an option to go to the Control Panel.
So enter that. (The Windows Key and E should allow for the same type of thing)
Once in there, go to "Taskbar and Start menu"
Make sure it is selected to display, and not to hide itself.
It should hopefully then work.
I hope one of these suggestions works. I am relying more on the first one to be the best soloution