» Thu Dec 15, 2011 1:56 am
If you have to... You can right-click on the game name in the library and choose 'delete local content' ~This will require you to re-download the entire game; but do you really need to?
Maybe try verifying the game files first. (Right-click the name >> click Properties, click the Local Files Tab, click Verify integrity of game cache). This will check everything, and re-download anything that is missing or corrupt.