Steps to re-enroll PGP Desktop.
1. Right click on PGP tray icon and click on Exit PGP Services.
2. Open Run and type %appdata%.
3. Delete the PGPprefs.xml file under PGP Corporation Folder.
4. Open Start>Programs>Startup>PGP Tray.
After following these steps the re-enrollment process would start for PGP Desktop.