i got this computer from a friend's dad, and it does not boot w/ its power supply, so i tried another power supply and it kind of worked. it turned on and started humming from the speaker, and the screen started to display horizontal lines going up and down the screen, but nothing else happened. also, it will not work if the battery is in the computer. if it is it turns off immediately. i have no experience fixing a mac this age, and would like to learn how.