1. Uninstall PGP Desktop: Go to Start>Programs>PGP and click Uninstall PGP Desktop. Or Add/Remove Programs in the Windows Control Panel can be used, and is the only way to do it if an older version of PGP Desktop is being run. (This step will not remove the keyring files.)
2. Transferring the keyrings can be accomplished by copying the keyring files (pubring.pkr and secring.skr) from the old computer to floppy disk, or some other removable media, and transferring them to the new computer. The folder for these files is C:\Documents and Settings\<user>\My Documents\PGP\. (If PGP Desktop has never been installed on the new computer, this folder must be created manually.)
3. To Install PGP Desktop on the new system, download PGP Desktop by clicking the download link in the original PGP order confirmation email.
4.During the PGP Desktop setup wizard on the new computer choose No, I have existing keyrings and point the setup wizard to the keyrings from the old computer.
5. Use the same name, organization, and license number used when PGP Desktop was originally authorized.
ref: http://www.symantec.com/docs/TECH148851