First off, this question may sound sacriligious to your hardwood floor gurus, but I have to ask to soothe my conscience.
We found hardwood floor under our carpet and tile. Once everything was removed, we found a section 3'x 2'on the half of the room where the nailing would have ended. The rest of the floor looks good enough to refinish.
Our flooring expert is telling us that we have to pull out the whole floor and that we can't just take a portion (or half) of the floor up and lay new wood.