All worked great : Maybe a part left over...

My Problem

After missing the "free replace harddrive" for this 2009 iMac by one day it finally started making a whining noise after 4.5 years of constant usage.

My Fix

Followed the iFixit manual and everything worked great. Replacing the harddrive were fast and easy.

However, as I assembeled the front plastic screen I noticed a thing looking like a "button" battery (CR?), 4 mm in diameter and 2.35 mm in height on the monitor screen.

Apples Timemachine worked flawlessly for restoring the data on the drive.

My Advice

Have some compressed air on a can to clean the inside of the mac before assembly.