Apple iMac G5, 20-inch - Manual (Page 171)

iMac G5 (20-inch) Take Apart - Midplane Assembly-Short Cut
24. Slide the optical drive into place and press down near the tab to reconnect the drive. If
the drive won’t click into place, check that the fan cables (near the connector) are out
of the way.
25. Replace the four optical drive screws.