When I dug my 2000 out of the loft recently I found the same thing. Battery had leaked everywhere. Cleaned up reasonably well, so rather than replace it with another one of those fixed barrel batteries, I found a 3.6V 280mAh NiMh universal battery with cables and terminal connectors. Solder a pair of terminal posts onto the motherboard where the battery came out, and instant easily replaceable battery.
