You get this message because your free tables are in Fox2.x format. You can use SYS(2029) to check table format. See Suppress DBC warning message Thread #593502 for related discussion.

>Hi,
> Just as background, the table can be opened in VFO70 with no problem
>delete and add rows, no problem as long as is a fee table. now we decided to
>create a database and want to include 'on the fly', but I am getting the message below each time the command ADD TABLE table1.
>
>File 'users.dbf' will be updated to a new file format, making it unreadable
>to previous versions of Foxpro. This can be reversed with a 'COPY TO'
>command, and the old table will be saved as a .BAK. continue?
>
>
>I click , since I don't want to change the table's properties.
>I think this is related to the table's code page, but if I run
>the command ?cpdbf() the value is 1252 which is the same as
>?CPCURRENT(1).
>
>So how can I avoid this message?
>
>Thanks!
>