Windows live movie maker might support mp4 format. It supports more formats than the old windows movie maker. Also, I would definitely try live movie maker before getting anything else, particularly something you pay for. It's actually a great program with lots of creative potential. I've used Premier Pro before and for most everything I prefer live movie maker (I've also used windows movie maker, the old version). It's the simplicity of the program that I love. Also it has way better output options than the earlier version. But I do very simple videos these days, mostly of people, sometimes mini interviews. The only shortcoming for what I'm doing is that it would be nice to have the ability of laying down other sound tracks in case I'm using more than one mic along with a separate sound recorder. But there is a program called "dual eyes" that takes care of that problem (it's not free, though) which I might get in the future. I would prefer that route than having to use a more complicated editor such as Premier Pro. But those are just my own needs. Since it's free, I'd try live movie maker and judge for yourself. Also you can download free trial versions of other editors that cost money and see how they compare with the free ones for your own needs. Just because an editor has way more options and possibilities, these come with a price both in terms of money and in terms of a learning curve.