My monitor Display is Upside Down

This morning there was a pop up on my desktop that said there was a dell support upgrade available.  When I downloaded it there was an error message that said it couldn't be completed because there was an exclusive file in use.  I couldn't close any of the windows so I did a control alt delete and shut down.  Now my display is upside down.  Don't know if any of the above is applicable but how can I get the display back to normal?  Any help would be appreciated.