First, you need to take the cover off. There's a single screw on the back panel, it's at the top and in the middle. Remove it. Push the tabs at the back of the computer and tilt the cover up and off. Don't tilt it too far though! Disconnect the cables from the floppy drive(s) and the hard drive. There are 4 screws that hold the assembly that has all of the drives on it, remove them. Then take the assembly out. Disconnect the cables from the motherboard and remove the reset/interrupt switch if necessary. Remove the 2 screws that hold the logic board in. Press the tabs that hold the motherboard in (there are 9 of them) one at a time and lift the motherboard up slightly each time. Finally, slide the logic board toward the front to clear the ports from the holes and take the logic board out.
Disconnect the power and SCSI cables from the hard drive. Remove the 2 mounting screws. Lift the back of the drive first, slide it toward the power supply, and remove it.
CD-ROM Drive/DVD-ROM Drive
Take off the cover. Disconnect the floppy cable from the floppy drive(s). Remove the screw that holds it. Lift the back of the drive, slide it backwards, and take it out.
Information provided by Doug Brown.