Apple Recalling "Some" 1TB Seagate Hard Drives

"Apple has issued a recall for a "small number" of 1TB Seagate hard drives in the 21.5-inch and 27-inch iMacs."

You can go here to see if your iMac is one of the affected ones, and if it is, you will be able to find out what to do from the same page. The affected units were sold between May and July of 2011, and Apple will replace the drives for free.