Thank you for your response.The "Do not merge, just add new records without merging" was an option I saw in version 16 after going into the Append/Merge.
I actually had tried to do a merge first by not enabling that option, and it came up with hundreds (or thousands?) of messages saying that records could not be merged because more than one match had been found.That's when I decided to try the other option, which I thought was saying "Do not merge [duplicate records, just skip them], just add new record records".I now understand it is just saying that it'll just add (append) *all* the records (even those that already exist in the file) as if they were new.
I just realized that I should have just merged the files and told it not to merge any of the "likely matches"... I'm assuming it would then just skip any of those records that it wasn't positive was the same individual, and then next it would hopefully give an opportunity to add all the individuals it found no match for (which are the new records he is trying to recover). I think I just aborted out of the merge process too soon.
I don't have the program, so I'll have to wait until I go to his house again to try it out.
And yes, I am doing all this with a backup copy I made of his files so that there's no risk in experimenting.
P.S. Sorry for the duplicate posting... my browser timed out and so I didn't think my initial attempt had worked.