>I had an old database which I zapped - then I went onto the web and downloaded a newer version onto my computer and put in in the original directory where the cdx of the old file still remains
>
>But if I try to reindex nothing happens - the downloaded file has the same fields as the original
>
>Why cant I reindex the downloded file

There's a byte in the header which says that the dbf has a cdx. The downloaded table probably has that to zero, i.e. thinks it has no cdx.

A simple trick would be to move the cdx to a different folder, index the table on just about anything, so it now has a cdx. Then move your cdx back, overwriting this temporary cdx, and then try to reindex.