Are you uploading from Videopad directly or are you creating a YouTube-format compatible video file and using their uploader?
If the former, try the latter.
If the project is exported as an mp4 video and displayed in a viewer on the PC, is the aspect ratio correct?
Share your project and someone will check it out. Here's how... http://nch.invisionzone.com/topic/23659-tips-for-getting-help-on-this-forum/