if it works, so I would suggest creating a copy of the movie you want to add transitions and/or effects to, and work off that. Doing it that way preserves the original for any errors you make on the way.
http://windows.microsoft.com/en-us/windows-vista/Add-transitions-and-effects-to-pictures-and-video-in-Windows-Movie-Maker
The link above shows that WMM will do transitions and effects on photos. Whether they will be good enough for you only you can tell.
I don't know VideoPad at all so I can't say about compatible file, (movie), formats.
But good luck and have a go.
Mark
I am using VideoPad software for the first time. I was disappointed to see that with still photos, the only transition effect offered is fade in. Is there a way to use Windows Movie Maker with my photos and then incorporate the photos with transition effects into my VideoPad project?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic