What version of Videopad is being used? How long is the project? What's the resolution of the bulk of the files? (Right-click on a file in the bin, click PROPERTIES, dimensions.)
Try exporting at a lower resolution, using AVI with the MPEG compressor.
Share your work here and someone will make a fix for you. This takes little time, and can be private. Just follow the PORTABLE PROJECT instructions here...
http://nch.invisionzone.com/topic/23659-tips-for-getting-help-on-this-forum/
If it contains sensitive material link it in a personal message (PM). Click the envelope above. It won't be passed on or retained. Use FILE|SAVE PORTABLE PROJECT AS, not simply SAVE PROJECT, and don't forget to get a shareable, public link to post.