I don't know anything about this stuff. But, i will tell you that windows movie maker + youtube hosting = mega fail (assuming you would put it on youtube)
Windows movie maker would rape the graphics, and pootube would just kill it. I highly recommend you get a non-free system like vegas.
Also theres also a need of compressing replays and crap such as that, (compressing the file would make it run faster) But if i'm not mistaken you aren't able to do that in movie maker, at least to my understanding of movie maker. I'm quite sure that someone will post something in the near future that will completely contridict what i just said. Cahnces are that they are right, and i am wrong. have a nice day =D