Not sure if you are using the latest version. Movie Maker is part of Windows Live Essentials 2011 and that's the one I have (even if I don't really use it much).
Not sure what I've done but went to open the 'windows movie maker' & it won't even open now!!! - neither the original or the video I started to make will open??? - Got that sorted now but still struggling to get music onto it?
Google for Windows Live Essentials 2011 and you will find the download link. It includes more applications than just Windows Movie Maker, but you can choose what to install once you being the installation.
Have you tried photobucket? You can even login with a facebook account if, you don't have a photobucket one. I tried to check limits on photobucket but found no info, so maybe it will work with your video.