1. Press the eject key in the top right corner of the keyboard. (Not present in a macbook air) 2. Drag disk icon from desktop to trash can. 3. Right click on disk icon and click eject. 4. Use disk utility to manually force unmount the inserted disk from within the superdrive. This will cause it to eject.

http://support.apple.com/kb/HT5523 This lists the specifications that the RAM must comply with to be compatible. http://support.apple.com/kb/HT5540?viewl... This shows the procedure to upgrade the RAM. The 27" and the 21.5" iMacs are different in that the 27" has a dedicated RAM compartment, accessible from the rear WITHOUT tearing open the screen. Hope this helps! EDIT: To find out what RAM your computer will work with go to http://www.crucial.com/uk/systemscanner/ and download the tiny application (Windows or Mac). After it's run it will send you to a webpage with an analysis of your computer and links to buy compatible RAM.