Currently Being ModeratedMar 17, 2013 3:06 PM (in response to Drew777)
You can use a Blu-Ray drive, but you need third-party applications in order to use Blu-Ray's. That's why I recommend you to buy an external optical drive instead, so this will be easier and you won't have to modify your computer.
If you don't want an external optical drive and your Mac isn't in warranty anymore, you can try installing a new optical drive. A new SuperDrive for a 21'5-inch iMac costs less than $100, and this is the compatible SuperDrive for your iMac > http://www.ifixit.com/Apple-Parts/12-7-mm-SATA-8x-SuperDrive/IF171-002 Apart, you have here the steps to follow in order to install an optical drive > http://www.ifixit.com/Guide/iMac+Intel+21.5-Inch+EMC+2308+Optical+Drive+Replacem ent/1775/1
Currently Being ModeratedMar 17, 2013 4:38 PM (in response to Drew777)
The CD drive on your iMac is the Sony AD-5680H. YouTube has plenty of information on disassembling your computer. Just be patient, not too rough, and follow the instructions carefully. I advise you to watch several videos, until you get the feel for the best method. I recommend memorizing the steps, so you're super comfortable.
Good luck and have fun!
P.S. You could also buy an external drive from Apple for $79.