Sounds like you have the iMac G3 (October 1999), probably the “Bonnie Blue”. To remove the hard drive roll her over onto her back so that the small plastic apple is toward you and inverted.. There is a screw where the recessed handle is, remove that. This whole bottom piece will now slide toward you With a medium sized flathead screw driver loosen the two large bolt type screws securing the video input in the center. To the left of that depress the black plastic locking tab and pull the power socket plug in. Now to the right you will see a small black strip plug in, there is a built in tool that you can grasp to help pull this plug with damaging the wires. Now remove the two screw holding this unit in place. There are toward you in the recessed shelf juncture between this place and the major housing. This whole unit should now slide toward you and detach. The hard drive is in this unit. Remove the CD ROM and then the hard drive will come out. It is held in place with two screws in a bracket. From here it would take a lot longer to describe than to do it. Just take all the screws out. If you need further hepl please let me know.