Attached Link: http://www.computerworlduk.com/technology/operating-systems/nix/news-analysis/index.cfm?articleid=1298&pn=2

This article says the nominal lifespan of hard drives is roughly five years.

Perceptions of this lifespan may be somewhat skewed by the fact that users tend to replace their computers/hard drives about every 3-5 years. A 5-year old hard drive has less than 5% of the capacity of an equivalent priced drive today. That means users tend to replace their drives before experiencing a major failure.

If a CD/DVD is unreadable, try reading it in the drive that created it and on an older computer. Compatibility issues may well be the culprit. Newer drives are optimized for fast disk burns compared to older drives.

A few years ago, I backed up 100 of my old Poser content CDs (upwards at that time to seven years old) and did not have a single unreadable disk (mostly TDK brand).  I've had one hard drive crash out of about ten internal hard disks I've owned over the years (on a 7 yr-old computer). My experiences won't match everybody's, but it makes me leary about betting that a hard drive is the best means of archiving digital data.

The jury is not yet out on external hard drives because consumer priced models haven't been around all that long. The oldest ones tend to get mothballed before they reach their terminal lifespan because of the speed at which larger drives hit the markets.

The scarier part of today's large drives is that a loss can mean losing over a terabyte of data.

My visual indexes of Poser content are at http://www.sharecg.com/pf/rgagnon