I had the same issue already in the past, what I did:
Disk decryption
pgp uninstallation
used "windows installer cleanup" to clean the "loop" installation process
regedit to remove all registry entrie from PGP > check HKML/software/PGP corporation and also in you HKCU/software/PGP corporation
Check your windows user profil about folder from PGP Corporation and remove it
For win xp : c:\documents and settings\username\application data
For vista and W7 : c:\user\username\appdata (check in all the folder displayed)
Reboot and re-install PGP
Cheers,
Lorenzo