Seen this on another forum...
When you use the iPad for shooting video, the correct orientation is home button down for portrait, or home button right for landscape. If you get it wrong, QuickTime will still play the video in the correct orientation, but other players will not. In Windows Media Player and VLC the video will appear upside down
QuickTime defaults to some crazy screen placement on the PC that I've never been able to figure out. Just go to View and select Fit to Screen, and the video will resize, until the next time you use it, when you'll have to do it over.