If DX-Ball 2 will locate the boards, depends on where you have installed them, and what version of the board pack you have installed, as there are two.
If you use DX-Ball 2 1.25, and have recently purchased Board Pack #1, it should work like a charm. Just be aware of the location where the game and board pack is installed:
DX-Ball 2 should be located in Program Files\LDA Games\DX-Ball 2 unless you've changed the path during the installation, which I don't recommend you do. Whatsoever, just make sure that any additional board packs are installed in the same directory.
As for Rival Ball, you'll probably have to edit the file dirs.cfg. It's just a text document containing the paths where Rival Ball will search for board packs under startup. If one of the paths indeed are identical with the one where you installed the game and the board pack, there shouldn't be any problems, unless you have the older version of Board Pack #1.
If you can't figure this out, I recommend you re-install the game and the board pack, but mind you--install them both in the same directory. If you appear to have the old version of Board Pack #1, I suggest you contact Jim at firstname.lastname@example.org