iPhoto 5 would predate your Macbook Pro, so that is a second odd thing to see. Do you have a copy of your software on an external drive to reinstall your original iPhoto? Time machine or a clone?
This is where a clone of your computer is a handy thing to have, to restore the computer as it was before some adverse change caused problems.
You can custom install iPhoto directly from the discs that came with your computer. iPhoto is either inside the Bundled Software folder or the Application folder.
Updated Security for Snow Leopard 10.6.8 now IPhoto app gone. System says install IPhoto 5. Really? Please tell me where that is located?