I am trying to load clips in movie maker from a gopro.  The clips will play in windows media player but the bigger clips will not make it past the preparing step in windows movie maker.  It shows that the file is corrupt and needs to be removed.  Is there a way to edit or shrink the video prior to using movie maker?  gopro software had the same issue.  If the files will play in windows media player why wont they work in editing software?

Thanks

Brian