bghoo8313 describes how to swap an imac G3 hard drive. Unscrew knob on the hatch on the back of the computer unit. Remove the RAM and the card. Take out 4 screws, 2 on the top and the other 2 under the guard. Pry it open with a screwdriver. Take out the outer screws under the guard. Open the unit from the "Apple" logo on the back. You will hear snaps, but the unit is not damaged. There are 6 radiation screws, take them out. Use a magnetic head screwdriver to avoid dropping screws. There are 4 screws that hold the hard drive in place. Remove them to take out the hard drive. Put in a new hard drive and screw everything back together to hold it together in place. Finally, put everything back together to have a functional computer unit. Boot up the imac computer to test the functionality of the new hard drive.