iMac between May and July 2011 sporting a 1TB Seagate HDD? You should probably know that the platter might be of the prone to failing variety. No worries though, Apple's announced it'll replace potentially faulty drives at no cost to keep ya smiling, and your fixed disk a-spinnin'. Owners of registered rigs at risk are being notified via email, but if you skipped that form you can check the serial number on Camp Cupertino's website (linked below). After confirming that the machine's eligible, you'll be able to drop it off at an Apple Store or authorized service center for the swap. It's also suggested that you back up the drive prior to bringing it down; at the very least, it's an excuse to make use of that Thunderbolt port, right?