Nobody replied to this question (although 132 viewed it) so I sent it to support at ShopBot. Frank answered and said, "The main two files are the ShopBot.ini and my_variables. The config file location is going to depend on your version of windows."

The "my_variables" file was pretty obvious to me, but the shopbot.ini was harder to anticipate. Turns out it's the one with with the variable units for your steppers. It's harder to find, too, because in Windows 8 the folder where it lives is "hidden" in the default installation. You need to change file view to display hidden files and folders.

Running Windows 8:
shopbot.ini is in (your root hard drive)\ProgramData\ShopBot\ShopBot3
my_variables.sbc is in (root hard drive)\SbParts\Custom

I hope that's of help to somebody who suddenly has to jump to a new computer in the midst of a tight work schedule, which is where I was.

Mike