All my icons on my laptop and start menu are gone..help?

I have a compaq laptop. When I turn on my computer, the start menu, task bar, and all my icons show up like normal for all of 5 seconds, then everything goes away, all that is left is my backround picture. There's no task bar, menu, nothing! I turn my cimputer off and start it up again and it does the same thing. Any advice or help?? Im guessing I have a virus..but just trying to see if there's anything I can do to try to fix it. Thanks
 
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