Files with the extension PIP are used by Microsoft Office for settings.
They contain the settings for personalized mens and toolbars. These are generated by each Office application based on the most used Meneintrge. As a result, only these will be displayed after some time.
The files contain the application they created in their name. So eg Word.Pip or Word11.Pip.
The user settings can also be directly influenced under Word Options-> Customize.