meanwhile, the Leading Edge Model D I bought in 1985 is still working..;)
The battery they're talking about is the CMOS battery (or was back when I replaced them). They look like big watch batteries, or sometimes smaller watch batteries..;) What it does is keep your BIOS charged up, time and date, settings changes, etc. Usually there's a small plastic holder for it, and it pops out.

Definitely hold on to the hard drive if you junk it, as mentioned above. Also, any cards you might have put in (PCMCIA cards, slide in the side), if you have any. Memory will probably be a wash, since that's usually specific to the mobo as well. Standard accessories that use USB, video, etc., you can transfer, but the external power supply is probably also heading to that big crusher in the sky. And you can keep the bag it travels in..;)

I wish I'd said that.. The Staircase Wit

anahl nathrak uth vas betude doth yel dyenvey..;)