If a winner's name was entered into a contest incorrectly a user can remove the win from the winner's history with a few clicks.

Go to Front Desk > Listener Database > Listeners and look up the winner. Go to Listener History and click on "distribute" for the contest win you wish to remove.
When you see the contest details click the red 'X' on the toolbar and confirm that you wish to remove the contest win.

If this winner was entered in-studio and you wish to free up that contest play for use for another winner you can unlog it.

Go to Studio > In-Studio and use the green arrows or Browse Log to navigate to the contest play. Then click the red checkmark icon to unlog the contest play, allowing it to be used for a new winner.