The only Videopad file of importance to the user is the VPJ control file that tells the program where to find source files and how to make transitions/effects/etc.
That file is generated when a project is saved. Save Project File AS routinely, giving it a unique # or name, so as not to overwrite prior saves. Using Save Project Files (no AS) will overwrite.
But now you know not to move or delete your source files until certain that the project will never be loaded again.