After installing this cool new Windows Media Center plugin, "Movie Browser", I noticed that its data store uses a proprietary XML schema, so I wrote a quick and dirty console app to generate the XML data file based on a common directory structure containing MyMovies.xml files used by My Movies and many other plugins. Of course, the developer has said he will eventually support the MyMovies.xml format, but until then...
The app was written in .NET using Visual C# 2008 Express Edition (using LINQ and other 3.0 stuff if you're a developer type). You can download a copy of the source or the .exe directly. It requires .NET 3.5. And the usual disclaimer...the app was only tested on my machine using my movie collection. It is not supported, it may hose your machine, YMMV, etc....blah, blah, blah.
To run the app, open a cmd window (run as administrator on Vista) and type something like the following. It will create a backup of the output file if it already exists.
MovieBrowserMetadataTranslator.exe "C:\\MovieCollection\\" "C:\\Windows\\ehome\\MovieBrowser\\Recent.xml"
Enjoy!