Sometimes a game can get corrupted during download. Please un-install the game, re-download it, and completely re-install it.
If that does not work, sometimes your computer may remember the old corrupted download. Please follow these steps to help force your computer to download a fresh copy.
1. Close all your web browser windows.
2. Clear your browser cache.
In Internet Explorer, go to Tools, select Internet Options, then hit the Delete Files button under Temporary Internet Files. This will remove cached files from your machine. In Firefox, go to Tools, select Clear Private Data, make sure Cache is checked, and clear private data now. For other web browsers please consult your browser's Help system to learn how to clear the cache.
3. Save the installer to a NEW location. Please follow the original instructions to download and save your game, but save it to a DIFFERENT LOCATION THAN YOU DID BEFORE. If you saved the game to your Desktop, save it to a folder on your hard drive instead (for example). Once you have saved the file to this new location, run the installer to put the game back on your computer.
If the above do not work, then your computer may be infected by a virus. Please run a virus scanner on your computer to see if there are any problems.