This issue can be resolved by contacting the PGP Universal Server administrator for further instructions if the client is managed by a server or by running the following command to decrypt the disk.

Windows XP  

1. Click Start>Run.
2. Type cmd in the Open field and click OK.
3. Browse to C:\Program Files\PGP Corporation\PGP Desktop
4. Type pgpwde --decrypt -p >passphrase< --disk 0 --all-partitions

Windows 7

1. Click Start>Run.
2. Type cmd in the Start Search field.
3. Click cmd from the list of Programs.
4. Browse to C:\Program Files\PGP Corporation\PGP Desktop
5. Type pgpwde --decrypt -p >passphrase< --disk 0 --all-partitions

 For PGP RDD clients:

If you find that PGP RDD is enabled on the Group Policy for the user and decryption cannot occur, use the following steps to decrypt the disk:

1. Create a new group on the PGP Universal Server and name it "Decryption Group" or something similar.
2. Create a new policy by cloning the default policy.
3. Edit this new policy and remove RDD functionality from it.
4. Save the policy.
5. Add this policy to the Decryption Group.
6. Move user to the Decryption Group that you created.
7. Have the user "Update Policy" from PGP Desktop and attempt decryption.

More details on this can be found here.