I have an iMac with a failing hard drive (which Apple will replace as it's covered under their failing hard drive replacement program). But I need to back it up before it is replaced. Utility notes that it is "failing," but it is still functioning. However, when I try to back it up to Time Machine, it only makes it through about 10GB before freezing and requiring a hard reboot, losing all backed up info. Is there some trick to prevent this from happening? Keeping it from freezing? So that I can make a back up before replacing the hard drive? Thank you!!!!!!!!!!!