Partitioning mess/Unallocated drive/I wanna cry

I got a 3TB external harddrive but I can't use it to play movies or anything on my DVD player or an Xbox 360. I was told I need to partition it. I figured out how to do this except when I split off the first partition of 440GB it also made an unallocated drive of 746GB that I am unable to do the "new simple volume" action with. Is there a way to put it back together? Surely I'm not going to just lose almost a TB of space am I? I am not the computer whiz of the family and I'm afraid I screwed somehing up bad. Should have just left it to my brother perhaps. Please help!