Movie Transfer to USB HDD

So, I have a 40gb appleTV and have loaded it with songs from iTunes and downloaded avi movies from cyberduck. I just hooked up an external 1tb hard drive and configured it. Itunes is currently loading all the songs onto the external and iTunes shows the 1tb of memory. My question is how will i transfer movies I have downloaded to the external hard drive? Will transferring them as usual over cyberduck into the movie file put them directly onto the external now? if not how will I do this? I question this because I still have access to all my movies which are on the internal 40gb hard drive even though I set up the external as primary hard drive. By the way I use sapphire to play my movies, thats where my files are currently available and thats where I want them to be in the future.