I was reading the suggestions about the conversion between SDII and WAV
(which direction the coversion was supposed to be done was a mystery yet),
and I decided to try to clarify things a little.
1. A lot of audio software for the Mac already read WAV format. BIAS Peak,
Macromedia Deck and Digidiesign Sound Designer II itself read and write WAV
format files.
2. Also there is a lot of software in Windows which read and write AIFF
files. Since AIFF format is very common in the Mac, you can use this to make
the transport, and, once in the Mac environment, it would be easy to
translate it in SDII.

Therefore, my advice is - If you want to transfer files to/from Mac and PC,
use the AIFF format. It is perhaps the best one to do the job.

If you are in PC, and just downloaded SDII files - A-Wave does the job (so
far it was the only one that reads SDII - and it is shareware). However
there are several more which read SD (the first one).