Same plist is being used for two different apps!

I've been working on a new project based on an old Unity project. I have renamed the project at the folder level, and have changed the name in Player settings. But when I built the project on the same computer that the previous project it was built on, it was populated with the information stored in the plist for the old program.

I want to have both working on the same computer, but now having used the new program on the same computer as the old, it has wiped the plist information from the old program and replaced it.

How do I force the program to use a unique Player Prefs plist?