Windows Movie Maker project not opening?

I had to make a movie on Window Live Movie Maker at my school. The computers at my school run windows 7, and so does my laptop. I emailed myself my movie from school, and when i tried to open it at my house, windows movie maker says "Sorry, Movie Maker cannot open this project file. The file may not be compatible with Windows Live Movie Maker or may be corrupt. Please select a different project file." Does anyone know why this is happening and how to fix it?