The Files folder has "snapshots" of shapes, graphics and photos as placed on the page.
I just checked a few files to be sure of this... If you put a photo on a blue page (for example) and add a drop shadow to it, the photo saved in the Files folder will have enough blue showing around it to save the shadow as well. If you wanted to use that photo again on a different background (and maybe without the shadow), you would need to have the original photo. So make sure all original photo versions are in there – don't delete original stuff to save space in there

As for photo albums, slide shows, form backgrounds and submit buttons... those images will not be in the Files folder. They'll be referenced from their original locations. That's why I like to create folders for graphics, images, etc. and put those within a main folder which includes the .vnu and Files.
You only have to transfer one folder and everything is in it, just like it was on the first computer. No problems with "File Not Found" when uploading

Thanks Paintbrush, that helps me understand how it works a little more too. I personally also have a specific folder location that I keep all of my projects in and I would just copy the entire project file for any sites I'm trying to transfer. I'm assuming that would work for VSD also, but I don't know the file tree structure and what is or isn't saved in separate locations etc. Now I have a much better idea, most appreciated

I've learned the hard way to clean up my computers and keep things organized