After making a backup of the file, and then another one in a different place

Take a copy of the file and you can use the LLFF to manipulate the header of the file to lower the number of rows (N) in the file to the point where headersize + N * recordsize be be something less than the 2gb limit. Then you'll have to use to truncate the file to the size. You can use the DBF file structure documentation from the help file as a guide to where the number of rows is stored and how to determine record size and header size.

>We have a dbf that is too big. How do you open it when it won't open.