How to get a movie off of imovie onto my computer?

I have no space left on my iPhone because of my movie I made on imovie! I tried to download it on to my computer, which is not a Mac, but it wouldn't work. I would get it to copy though iTunes but when I would try to play it back on iTunes, Internet, and other players it wouldn't work because it was "unsupported" I also tried to put it onto a disc but the cd was too small. I can't transfer it to my camera roll then put it on my computer because I don't have room. The only way I can free room is to delete a bunch of pics off my phone, but that means they'll delete off of imovie too. Any help? Sorry I'm not good at explaining anything haha

Set up an iCloud account and back up your phone there. Then download iCloud for Windows from

http://support.apple.com/.../kb/DL1455