InterDrive Error

One of the Win95 clients where I work gets this error every time at startup:

InterDrive PP Error
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InterDrive has not been loaded

I can’t find *any* reference to InterDrive anywhere. Yet… I get the same error whenever I right click for properties on a drive icon in Windows Explorer. Except, the header on that dialog box reads InterDrive 95 instead of InterDrive PP. Is anyone out there familiar enough with InterDrive that can help?