Problem
On your Mac, you have downloaded the Mac OS X Lion upgrade but need to download it again as the file may have become corrupt or was interrupted by your internet disconnecting. Also, you may have already installed Lion but would like to download it again as a backup.
Solution
- Quit the App Store.
- Go to your Applications folder.
- Delete the “Install Mac OS X” file if it exists.
- Delete the “InstallESD.pkg” file if it exists.
- Open the App Store.
- Hold the alt key and click on Purchases (at the top).
- Next to where your Lion purchase is, hold the alt key and click Install.