Thrown the PC/console out of the window... problem solved! What I used to do when I was at school was do half an hour's work and the half an hour's Unreal Tournament and it seemed to work for me. Now I'm older I seem to just have the self control not to let it tempt me but self control is a very difficult thing to develop!
if u have a console, then lock it up in a trunk or cupboard. If u have a PC, uninstalll the game and remove the installation setup from ur pc. these are some simple things to do to overcome game addiction.
Id advise you work and set yourself reward time for your game.... do some work/play games for 10 mins etc..