When you say a moviemaker file, do you mean the finshed movie file or are you trying to put the unfinished project file into powerpoint (which obviously won't work as the movie is unfinished!).
Moviemaker saves the project files with the extension . MSWMM. When you have completed the movie and go to save finished movie, you get to choose the format (to a limited degree) and the size.
Have a look click here to see about inserting a movie into a powerpoint presentation.