received email my imac hard drive needs replaced how do I backup my hard drive

Welcome to the Apple Support Communities

http://support.apple.com/kb/HT1427

You can also clone the drive with Carbon Copy Cleaner

Errr…

CarbonCopyCloner I think you mean…

There's also SuperDuper.

Forgive my curiosity, but where did this email come from and how could the sender know your HD status??

@noondaywitch The emails are from Apple. They know the what type of hard drive is installed in the machine by the serial number.

This is why it is always a good idea to register your system with Apple.

Ah! It's a recall. Always good to know the full story.

BTW, I wouldn't use Time Machine for this; stick with a bootable clone.

Apart from the third-party applications mentioned, you can also clone using Disk Utility's Restore function.

Use CarbonCopyCloner to make a bootable clone on an external drive and then wipe your internal hard drive before turning it in so no one will have access to any of your data.

See https://discussions.apple.com/thread/4449562?start=0&tstart=0 for more on backing up and the recall.