Jeffrey,
If you're looking for a third-party program for merge-purges, I'd look at either Superdup (lightweight but good) or DoubleTake (sophisticated).
I've never seen any good, comprehensive de-dupping utility for building into a foxpro app. I've written quite a few utilities for finding dups in various programs but the requirements were always differn't enough that I ended up with something differn't each time.
You can get either programs from Mailer's software
www.800mail.com