Upon startup, Windows tries to configure PhotoGallery, which I have uninstalled. Then a dialog box opens to ask for the CD-ROM. When I cancel, I get Error 1706. (no valid source for PhotoGallery). This repeats again and I go thru the same process. The PhotoGallery software never loaded correctly after several attempts which is why I dumped it, but this residue is bugging me. Where can I find the leftover files to eliminate this from happening?

There are several ways to do this.
#1 check your program folder in Windows to make sure all traces are gone from there.
#2 if you feel comfortable messing around in the Registry file, you can do a search for the name of that program and delete all references to it in there.
#3 if you don't feel comfortable messing in the folder then you can download a program that will get rid of the leftovers for you.
You can get a program here that will do the job for you. http://www.majorgeeks.com/download.php?id=15&sort=7

If you know nothing about the registry file, then grab a program. One error in deleting things will lead to reinstalling Windows.
Also, always make a backup of the registry before you do anything to it.