According to the below Virtual Disk backup guide, recovery and access to a Virtual Disk requires the passphrase alone (as it suggests anyone with access to the .pgd file can open it if they can guess the passphrase):
http://www.symantec.com/docs/TECH149289
On a related note, the uploading of keys to keyserver.pgp.com only uploads your public keys to aid others in contacting you. It does not help in anyway with recovery of data in the event you reinstall Windows. For that you need the private keys, whcih requires a slightly different backup method:
http://www.symantec.com/docs/HOWTO42075