CodePlex has a GUI tool for VSSConverter (link). Unfortunately, there hasnt been any development on the tool for a while and it does not work with Team Foundation Server (TFS) 2008 (the app does not start up with TFS 2008). What I found out was that the tool does not work because it was built with references to TFS 2005 dlls.
Below is the same tool rebuilt with references to TFS 2008 version of the DLLs. I have tested it and it works without a problem.
Just remember to copy the “VssConverterGui (TFS 2008).exe” file in the zip file to the Visual Studio 2008 install folder (typically “C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE” folder and this folder should contain VSSConverter.exe). Double click it and it should startup.