Here it is - the original iMac, aka the iMac G3

Place the iMac upside-down so you can easily access the bottom cover.

There is one screw holding the the bottom cover in. Remove it, and then pull on the handle to remove the entire bottom cover.

Locate the video cable, motherboard power cable, and auxiliary power cable.

Unscrew the video cable and remove it, and remove the other two cables.

Slide out the logic board tray, and remove it from the system.

All of the contents of the logic board tray can now be removed.

The CD drive can be slid out of its slot, and the hard drive is underneath.

The logic board can be removed by removing several screws holding it in.

The logic board is connected to a power adapter underneath, be sure to carefully detach it as you are removing the logic board.

The bottom plastic cover can be unscrewed and unsnapped. This will require some force, so be careful not to break any of the plastic.

Remove the speaker cover by carefully unsnapping it.

Remove the plastic bezel by unsnapping it.

The top cover (in this case, pink) is held in by two screws at the top of the computer. They are hidden under plastic covers, and must be removed before you can unsnap the top cover.