Windows Movie Maker Help

I've just gotten started with using this program and I feel quite confident on how to make basic videos/video editing. However, the one thing that I do not understand how to change is the resolution of the video. Whenever I am done wtih a video, I save it, and then this little window pops up stating the name, profile, etc. When I look at what it says under "profile" its says 320x240 at 30 framerates. How do I change this video size into somthing larger like 800x680?

Unfortunately you can't get the screen resolution any bigger than 720x576 - Video For Local Playback (1.5mb PAL).