Sad but true; the presently available PGP (GnuPG etc) won’t run on Windows 64-bit machines. Not the frontends, nor the key-handlers, nor the encryption-engines.
The problem with the commercial PGP—besides the price—is that the PGP development is nowadays driven by the companies that implement it. Anyone will understand that enterprises are not interested in endpoint encryption but in gateway encryption. The employee syncs via SSL or pre-shared, smartcard-certificates (which is for the communication sector) and the servers talk PGP. This way, no employee can hide information from their company and virus-protection can be implemented on the gateway.
I recommend using S/MIME with certificates. If s.o. doesn’t like to buy TTP-certificates (trusted 3rd party) from Comodo, Thawte, Global-Sign, Veri-sign, etc., he could join a WOT (Web-of-trust) like CA-cert. The only disadvantage is, that friends and commercial partners have to be informed in advance, that getting the CA-cert root-certificate is required (it is not pre-installed in Windows/Mozilla out-of-the-box).
Regarding convenience, that won’t make a practical difference. Using PGP requires all commercial partners to pre-trust the keys and to pre-consider which of their friends they trust. In my opinion, that is the equivalent to informing friends and commercial partners that they need the root-certificate and that they need to check fingerprints (same as PGP).
PGP enthusiasts should at least once in their lifetimes generate a key from someone in their "friend-trust", sign it and forward it to all others (even to the one who is the faked owner of that key). I predict, before the faked key is blacklisted, almost half of the PGP-friend-trust is already using that key.