News of the extension, first reported by MacRumors, was posted to Apple's Support webpage sometime on Friday, which noted email notifications were being sent to affected iMac owners who took the time to register their products. Users can also check the program's webpage to confirm eligibility.
From the announcement:
Apple has determined that certain Seagate 1TB hard drives used in 21.5-inch and 27-inch iMac systems may fail. These systems were sold between October 2009 and July 2011.
iMac owners who were affected by the Seagate-specific failure can have their hard drives replaced for free from Apple or an Apple Authorized Service Provider, or those who have already paid for repair or replacement can contact Apple for a possible refund.
First initiated in July 2011, the recall originally ran through July 23, 2012 and covered iMacs sold between May 2011 and July 2011. The program was subsequently extended for an additional year. With Friday's announcement, the replacement plan has been broadened again, and now covers affected iMacs for three years after the first retail sale of the unit or until April 12, 2013, whichever provides longer coverage.
Seagate's storage components were at the center of another fiasco in 2007, when Apple acknowledged that a number of MacBook and MacBook Pros shipped with faulty hard drives. An apparent manufacturing flaw caused the drive head of some units to permanently fail, scratching the disk patter and causing permanent data loss.