on the keyboard there should be a key marked "Fn" (stands for Function) amongst the F keys along the top F1 F2 etc there should be one with the symbol of a screen on. normally round F9 F10.

Press Fn+F10 (or whatever the screen key is) - if nothing happens press it again.

what this does is switches the screen from laptop to external VGA

he's either switched the scren -easy fix
OR
it's a hardware issue - £££