What happens when you right click anywhere on the desktop?  If you get a menu make sure under "arrange icons" the show desktop icons is checked.

Otherwise if nothing there is working you may have a virus. Try booting to safe mode (press F8 repeatly during retart to force menu).  If you can get to safe mode and you have icons and a start menu - go to run and type msconfig.  Then on the startup tab menu uncheck anything that looks strange.

Ironically I have the same problem right now (happened around 8 pm tonight ) and I am in the process of re installing windows right now.  I did trouble shooting for 3 hours and finally called tech support.  Corrupted windows files are the problem.  I'll probably spend most of tomorrow reinstalling all the programs.