hey guys. im putting together a short film and im getting aload of footage from other riders  but im only using the windows movie maker and some of the files are quick time and it doesnt suport them. how do i convert them into a usable format (free if poss), ive looked round google but i have no clue as to what i am looking for??? or is there a better editor i can get for free from somewhere that will automatically suport all formats? also im not that computer literate so if you could dumb down the technical jargon that would be a bonus 
thanks