Most of my personal data is stored on an external USB hard drive. When I recently attempted to access the drive a message appeared saying that the drive is not formatted and asked whether I would like to format the drive. I quickly realised that formatting the drive would result in all data being lost, so I declined the invitation. However, I am now in the position of being unable to access all the data on the drive. I tried rebooting the computer, changing the USB port to which the drive is connected, all to no avail. Do you think the fault lies with the external hard drive or computer? Also, is it possible to retrieve the material from the drive?

This is certainly a tricky situation, since you have mentioned that most of your personal data is stored on the drive so retrieving that data is likely to be quite important to you. You are correct about asking whether the problem is with the drive or the computer, so we need to make this determination before proceeding any further. Most likely, the problem is with the drive since it is a mechanical device which is potentially subject to failure. The best way to determine whether the problem lies with the drive is to connect that drive to a different computer. Any other computer running the same (or greater) version of Windows as your computer should be fine.

The most likely scenario is that the other computer will not recognise the drive either, and present the same outcome as when the drive is connected to your computer (i.e. the message informing that the drive is not formatted). In this case there is either something physically or logically wrong with the drive itself, most likely a form of corruption making the data unreadable. In this situation you should immediately disconnect the drive from the computer and not do anything further with that drive, since further experiments or attempts at data recovery are just likely to make the problem worse. Instead, at this point your only remaining option would be to consider professional data recovery. As per my previous point, I have recommended that you do not do anything more with the drive yourself. This is because we don’t want to make the problem worse for the professional data recover company, since that will likely make the data recovery process more difficult and costly. I imagine that in this situation you will want to take the professional data recovery route given the importance of the data. Generally you send away the drive and the data recovery company provides a quote (which may attract a small fee) for the data recovery. If you wish to proceed they will then recover the data to other media (such as a series of DVDs or, preferably, an external hard drive) and send the recovered data and original drive back to you. Two of the better known companies that handle data recovery are DriveSavers (www.drivesaversdatarecovery.com) and Kroll OnTrack (www.ontrackdatarecovery.com.au). Should you wish to use the services of a professional data recovery company I suggest that you use these two websites as a starting point and see whether either of these meet your needs.

Should you find that the problem does not occur when you connect the external drive to another computer then this would be a very strange situation! In this case I think that it is more likely that the drive is sporadically working rather than this indicating there is a problem with your computer. As such, if the drive is readable on the other computer you should seize the moment and copy as much data as possible from the external hard drive, as you don’t know for how long the drive will continue working! Once you have copied the data off the drive onto your computer I suggest you purchase a new external drive which you can copy the data back onto and use as your new primary external drive.

No matter which of the scenarios above you fall into, this situation is a good example of how external hard drives are susceptible to failure. Therefore, do not store your only copy of important data on your external hard drive – make sure you have a backup of all that data as well. In most cases modern computers have plenty of space on their internal hard drives so you can often store all of your data on the internal drive(s) and then just have a backup on an external drive. Additionally, if you want another level of redundancy on your internal drives you could consider setting up a RAID (redundant array of independent disks) configuration of drives which provides for redundancy of hard drives – essentially allowing you to setup the drives in a certain configuration to tolerate the loss of a certain number of hard drives. More information on RAID is available at en.wikipedia.org/wiki/RAID.

However, if you do want to use an external drive for the data you can purchase external drive enclosures which allow you to have multiple drives within the enclosure and run a RAID configuration or alike. This could be as simple as having two drives which mirror each other (RAID-1) allowing for one of the two drives to fail without any data loss. Alternatively, if you want more than two drives with redundancy, so that you can have both increased storage space and redundancy, you could consider a higher level of RAID (such as RAID-5).