It is very much possible and really easy to do. After the HDD in my VAIO Pocket failed I replaced it with a 60gb hard drive. My partner and I each have both a VAIO Pocket and NW-E507 players. Our music collection is around 30GB which has kept us from "upgrading" to one of the newer Sony players because we both really like the fact that our entire music collection is where ever we go, either on the VAIO Pockets or on our laptops. We use the NW-E507s for the gym or jogging etc but everywhere else it is the VAIO Pocket. People were floored by the album display and navigation and were disappointed when I told them that Sony does not make this jewel anymore. As for replacing the HDD, First unregister the player from SonicStage, then make sure you are grounded. After that remove the screws holding the battery cover on, then remove the battery cover, back cover, and battery. Remove the Hard Drive, Plug the new one in, reassemble, then use the format option in the VAIO Pocket menu, reregister with SonicStage, then move your music back (I did it before going to bed because it takes a while with as many songs as we have) then you are ready to go.
