Well, I have since rethought my strategy... however, putting the old drive in allows the CD/DVD to work again.
The drive was on cable select, but in the cube the only other drive is the CD/DVD... so would it disable the CD because it can't read the cable select?
I thought it was having issues because the an installation of Panther was on the HD but now that makes total sense... it hasn't even read the HD yet and the CD/DVD doesn't work.
Kudos!