I had written about a vista file deletion problem some time back. Vista would not allow a certain file to be renamed / deleted / moved. This happened to mostly DWG and RVT files that are more than 3 years old.
The happy news is that if you installed the web update 1 for the Revit 2010 versions, this problem should go away. If you still have this problem, please file a support request with Autodesk.