Help! Movie maker wont open

Hi, my daughter has a school project where she had to make a book trailer using movie maker, she created it on a laptop at school using windows 7 and saved it to her USB drive brought it home worked on it at home on her laptop which uses windows 8 saved all her work and took the USB back to school next day and now can no longer open it at school, she gets a error message saying something about file may be corrupt or is in use on another computer. We have tried renaming files, saving it to computer and emailing to herself instead of using her USB drive and still gets the same error at school but works fine at home and she has to present this movie in a few days at school if anyone knows of any possible solutions please let me know. Thanks