If you mean to creat one CD that can be used on both Mac and PCs you need to make two CDs. director8 files can be used on both platforms, but a projector file can only be used for the platform it is created in.
therefore make a projector file on a PC, move the Director file to a Mac and make another one.
Hope this is useful to you.
I have only learned Director8 this Semester, so tell me if this was useful
Antony