problems with gnupg-pgp

[Nuno Donato]

hello

i've recently installed gnupg to be able to communicate with some
persons who are using PGP (i like free alternatives :)
before installing i certified that both systems were compatible.
i sucessfully created my private and public keys and we exchanged
them. after that, i send a couple of test emails to another person
using GPG, and we were able to encrypt and decrypt the message.
however, i can not do the same with the PGP guys. when i try to
decrypt the message i get an error saying something it is not a valid
file...

i checked some docs and faqs, and found out that to have compatibility
the PGP version must be 5.x or higher.. they are using 8, so that is
not a problem.
what can i do to solve this? or to find out whats wrong..?

thank you very much
nuno donato