I may have deleted a process

Hi, I was playing a game on my computer the other day then it froze so I ctrl+alt+del but nothing showed up so (stupidly) I just started hitting other buttons but I think what I have done is erased an important process that makes the computer run properly (well thats how it seems because everything went wrong after then) so, with the game screen still up I just restarted the computer. When it was booted all of my icons and my start bar was gone I did a system restore last night to the point before all this happened and I thought I had fixed the problem everything worked fine. Then this morning all my icons were gone once again.

Please help me I'm out of ideas.