These steps will show you how to properly replace your hard drive on your Apple G5 Desktop.
Remove all the cables, including the power cables before opening the unit.
Lift the tab to unlock the side panel.
Remove the air deflector (the clear plastic cover) by pulling on the handle.
Locate hard drive on the top right-hand corner of the desktop.
Rotate up plastic tab labeled "B" on the right hand side of hard drive.
Detach both cables from the hard drive.
Pull out the hard drive out.
After hard drive is out, the space should look like this.