Cannot delete a XML Render Stylesheet

You want to delete a XML Render Stylesheet but an error occurs?
So this Stylesheet is in use, you have to do this:

• First delete the registration of the Stylesheet by opening it in the
  RichClient-Viewer an use the “x” new to “Registres Type”
• Use the General-Search and search for a Folder named
  ” StyleSheetCache”
• Expand this Folder and search for all your shylesheets you want to delete
  and cut them of the folder.
• Now you can delete the XML Render Stylesheet as normal.