Been gone from the amiga area for a long time.  Bought the new OS 4 without knowing I needed a PPC board.  My question is this; does the classic software (the kind that ran on the 2000's and 4000's that was programed before the day of the PPC cards)work on an amiga with one of these PPC boards installed?

I think he knows that already.

I don't own a PPC board, but from what I understand, there are some that come with a 68040/060 on them AS WELL as a PPC CPU.  These can run 68000 software just fine.

Then there are those that don't come with ONLY the PPC processor chip, and must use 68000 emulation to run the earlier software.  I don't know for sure, but there may be some compatibility issues with this.

Of course, in ANY case, you can usually disable the PPC CPU and revert to your Amiga's native 68000 (A2000), 68020 (A1200) or 68030 (A3000D) processor to run "classic" software.