Welcome, Always nice to see someone here my age

As for the battery, just cut the wires off it and use 3 AA or AAA batteries, the Rayovac 840 just has 3 1.5v cells in it (the same kind you would find if you disassembled a 9v battery)

Not sure if a dead battery would stop it giving video though, do you get a startup bong from it? I would try reseating anything removable on the motherboard (Ram, Vram, Cache etc). I know when my 8600 had been sitting around for a while i had to reseat everything to get it to fire up correctly