I appreciate you guy's answer, but all of that seem just speculation and nothing concrete as it does not make a whole lot of sense technically speaking but I'll be happy to be proven wrong. I also got to say that upgrading the HDD is quite possible, it's just not supported by bell and opening the devide will show that the size of the HDD is really what it is supposed to be. While the internal HDD probably have a partition reserved for menu system, interface, interactive guide etc... It's is not big enough to store all the on demand movie of the month without greatly reducing the available recording space available. If only I had that receiver I would test the theory myself by filling the HDD completly, removing the HDD and doing a raw reading of the disk on a computer to find how much space it actually use and what other space is left for other data. Also, the satellite can not just ''beam'' the rest of the movie even if a short buffer was already present on the internal HDD because that's not really possible with satellite technology (that's why Pay per view was the only option for a while).
As for not being able to use the full 2TB of a 2 TB HDD, it's actually pretty normal as a 1 TB HDD would format to about 937 Mb in your OS. Without getting too technical, let just say that the advertised capacity of HDD is not calculated in the exact same way as an operating system and file system calculate bytes, thus making you lose a substantial portion of the drive capacity you were expecting to have available when buying the drive.
One way to test your buffer theory would be to try to rent a movie without plugging the ethernet or phone line. You were still able to order pay per view event without having it connected up to a certain limit so it shouldn't be different if the system work in the way you guy are describing. Also, if you make an HDD format procedure on your PVR and try to watch an on demand movie right after it shouldn't work if your theory is right as the movie or buffer of the movie wouldn't be in the HDD yet and would need to be retransfered to the HDD...
Also, guide data is so small that it's not really much of a problem, it's only text based database and would only be a few hundred of KBs... Transferring that to the PVR HDD would never prove to be a problem as opposed to transferring a full HD video feature and is not very comparable to the video on-demand dilemma.
Last edited by SkinnyV; 2011-04-15 at 05:44 PM.