Apple iMac users are in for some good as well as some bad news.

The bad news is that last week, Apple admitted that some of the 3TB hard drives used in the company's 27-inch iMac devices, especially those sold between December 2012 and September 2013, may stop working under specific conditions. Users who bought their iMacs with the Apple Fusion Drive that pairs the 3TB HDD with a faster, but smaller capacity flash drive are the ones who are most likely to be affected. In fact, this configuration is mainly available for iMacs with higher specs and used by professionals requiring large storage capacity for their media content.

Now, the good news; the Cupertino-based tech titan has already started a replacement program for such iMac devices.

A report in Christian Today states that going by the post on the Apple's support page, the company has already started getting in touch with the affected iMac users via their email addresses that they provided during registration. On the other hand, users who didn't register while purchasing their iMacs, but think their devices need to be replaced, can make sure whether or not their units are covered in the replacement program. They can do this by using the iMac's serial numbers.

In addition, iMac owners can visit an Apple Store or any Apple Authorized Service Provider for the replacement. This apart, users who are of the view that their devices have already started failing can contact Apple Technical Support right away for a replacement.

Apple recommends that iMac owners who will go directly to service providers should first back up their data before getting a replacement. It is worth mentioning here that replacing iMac's 3TB hard drive will automatically set the device back to its factory settings. Besides rolling the data back, users will also require re-installing the operating system and other applications.

As of now, Apple is yet to provide details regarding how the 3TB hard drives on iMacs may possibly fail, but nearly all tech observers claim that the hard drives of the 27-inch iMac models may have been part of a faulty batch of hard drives, which was released by manufacturer Seagate some time back.