To get the case off, first remove the 6 screws from the back panel.
Next, use a screwdriver to pry the back apart from the top. You can then slide the case off.
Here is a picture of the case removed:
Next, put the computer on the side and remove any PCI cards by grasping the card and pulling upwards. Also, you have to remove the processor card right now.
Next, put the computer right side up again and disconnect all of the cables from the logic board. Here is a picture of the cables:
To disconnect the huge power cable, press the latch on it.
Here is a picture of the cables removed:
Next, pull out the power button. Also disconnect
the LED cable.
Pull the latch above the logic board to release it. The latch is circled in red.
Swing it out to the right. Then, take the logic board out.
Follow the steps from the logic board without pulling the board out (don't bother disconnecting the cables either). Then, disconnect the cables from the hard drive, push the clip down and slide it out.
Remove the case as described in the logic board section. Disconnect the 3 cables from the back of the CD-ROM drive. Pull up the clip under the CD-ROM drive and slide it out of the computer.
Remove the top case as described in the logic board section. Disconnect the floppy cable from the back of the floppy drive. Push down on the clip and slide the floppy drive out.
Special thanks to Tony Colter for the pictures!
Information provided by Doug Brown.