So I recently sold my Mac mini to buy a MacBook Pro off eBay, it just arrived today. I have pretty much everything set up on it just the way I like it, but there is one problem. If I go into the Mac App Store, It says Angry Birds needs to be updated, even though it is not installed. I then logged into my account, and that didn't fix it. I then tried to install my copy of the app, and then it prompts for me to log in to the previous owner's account. I deleted his credentials from the login box, and put in mine, but when I click "Next" it just gives me an error (picture attached below). If there is a file I need to delete or something, please say so. Any help will be appreciated.