Autodesk instructions:
http://knowledge.autodesk.com/support/revit-products/troubleshooting/caas/CloudHelp/cloudhelp/2015/ENU/Installation-Revit/files/GUID-2DC7BE05-FE32-4E49-BA43-6EED211DC6B1-htm.html
Use AutoDesk Uninstall Tool instead of Control Panel.
