How to revert whole disk decription

I have a 230GB disk divided in four partitions that I encrypted one year ago by PGP™ Desktop Version 10.2 for Windows. When I switch on the system I get the grey screen of PGP where I insert the password (I assume it is what you call PGP key). The password is the same of my Windows account and I am an administrator user of my laptop. Now I want to decrypt the whole disk and uninstall PGP but I cannot find in the Symantec site any instruction to do that. What's the fastest and safer way to decrypt the whole disk and remove completely PGP from my system?

Thank you in advance.