BIOS shadowing was introduced ages ago to copy the very slow ROM data into very quick RAM and used to give a massive improvement in performance. Some say it isnt needed any more as ROM has speeded up quite a bit so shaddowing is now unneccessary, but as it only eats a few KB of memory then it is too small to worry about.
Now about your booting problem ...
Try removing the battery and the charger.
Now press the "On" button and keep it held in for about 60 seconds.
Replace the battery.
Switch on in the normal way.
Is the machine showing any signs of life now?
I really appreciate kudos points as a payment for solving issues :o)