Before you drop a ton of cash on getting another video editting program I'd try two (free) options first:
1) Search around and see if you can find any way to do this is WMM. I didn't explore this option on my own as I had an easy means to get Sony Vegas. When I got vegas I stumbled across a way to fix it in vegas.
2) If that doesn't work, I'd look into free video editing software or even just try to find something that can let you do the editin gin WMM and encode it with something else.
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btw here is the guide I used on warcraftmovies:
WarcraftMovies.com - World of Warcraft Movies
Even if you don't get vegas, maybe some of the settings can help you figure it out on your own in WMM.