If you purchased an iMac between May 2011 and July 2011, you may be affected by a recent recall. Apple is recalling and replacing a small number of Seagate 1TB hard drives found in 21.5 and 27 inch iMac systems. If you’re unsure if your computer would fall within this recall, you can use your serial number to do a search here, and find out if you qualify.
For the replacement, you should schedule an appointment at your local Apple Retail store, or contact an authorized service provider. Be sure to have the original OS installation disc that came with your computer, as the replacement process will require a reinstall. And of course, be sure you conduct a full backup of your data before your hand your iMac to anyone, whether it’s your local Mac genius or your Uncle Bob!