The CPU is in a spring like socket like this:
http://www.ifixit.com/Teardown/iMac+Intel+21.5-Inch+EMC+2544+Teardown/11936#s42506
However it seems that there is also a square bracket over laid that is screwed down. Simply remove those screws to remove the bracket and the CPU falls out.
http://www.ifixit.com/Teardown/iMac+Intel+21.5-Inch+EMC+2544+Teardown/11936#s42506
However it seems that there is also a square bracket over laid that is screwed down. Simply remove those screws to remove the bracket and the CPU falls out.