You can use the iPhoto Library Upgrader tool to prepare your library to work with the current version of iPhoto or Photos for OS X.
When you open a library created by an earlier version of iPhoto, you might see a message that says “Library version too old. Please upgrade your library ‘iPhoto Library’ using the free iPhoto Library Upgrader available from Apple.”
The iPhoto Library Upgrader prepares libraries from iPhoto ’08 (v7.x) or earlier so that you can use them with the current version of iPhoto or Photos for OS X. If your library was created by iPhoto ’09 (v8.x) or later, you don’t need to use this tool.
I remember having to run this on customer machines back in the day if they had neglected updating to new versions of iLife on a regular basis.