Something wrong with windows 7, HELP?

one morning when i went to go on my computer i thought there was something wrong with my screen, later on i found out its not my screen for my computer but actually Win 7. ok so bastically windows on my computer is messed up, the screen desktop is slanted off to one side and part of the destop is missin and the other side there is a black bar. im pretty sure its not my actual screen but something wrong with windows 7 because once i turn on my comuter everythings normal but then i log in and the screen is missing . help! whats wrong and do i have a virus?