If your iBook is like mine (700MHz) The yellow screw was attached from the bottom through the bottom case and had to be removed earlier in order to remove the bottom case. Also the the green screw pictured to the left was missing already removed.
This photo is a little confusing. The shield should be off, which would show the correct positions of the yellow and orange screws. (The orange circle is in the wrong place.) Furthermore, these screws don't need to be removed at this stage (they hold the logic board to the frame). And finally, on my 800 MHz machine, BOTH these screws are 6 mm in length.
The two red screws and the orange screw have to be removed (iBook G3 600 MHz).
