Audigy and Audigy2 has different on-board connectors, wich are used to connect to it's 'Drives'...
While Audigy & Live! cards uses same AUD_EXT connector, Audigy2 series uses AD_EXT (note the difference

), wich is something complitely different...
In order to make old Audigy Drive to work on Audigy2, only thing that should be done is to make a custom cable...
If you have any interest doing this, check out these threads, just to learn about AUD_EXT & AD_EXT pinouts:
Soundblaster Live!, Audigy 1/2 and X-Fi* Pinouts
&
Creative Audigy 2 AD_EXT pin assignment
In order to make working cable, you should connect +5V on AUD_EXT to +5V to AD_EXT, GND to GND, SPDIF ins/outs to SPDIF ins/outs, etc, etc, etc...
Should not be very difficult...
P.S. Wish I had older AudigyDrive, so I could 100% verify this on my Audigy2, but some users confirmed this works, smooth as milk...