Why does Windows 7 assign the same drive letter to two external hard drives when they're plugged in simultaneously?

Question

I have two WD external hard drives. I want to use one for the lightroom catalogue and photo storage and then back up to the second. To do this I need both plugged in at once.

I have assigned a new drive name to the first one (z drive). When I open the second one my system recognises it as the same thing. On its own the second one will open as Z drive too.

I have renamed the external drives but that does not make any difference. I have tried to rename the drive on the second one to drive W. The next time I put the lightroom catalogue drive in it then renames itself to w drive.

I am using Windows 7, 64 bit.

Has anyone tried using a different brand of external drive in this situation??

Answer 1

It sounds like a signature collision, windows 7 handles things a little bit different. Because you mentioned all the details, I was able to locate a WD and win7 specific help for this problem. (I would have said IDs are the same, I dont know if that is the same thing?)

http://wdc.custhelp.com/app/answers/detail/a_id/6571/~/only-one-drive-is-seen-when-connecting-two-wd-external-drives-of-the-same-size

The basic information says: With both disks connected, check in Disk Manager for the missing disk, Find the "Offline" one, and observe that it has a "signature collision" Just right click and bring the disk "online" and the system will give it a new signature.

It also said Make sure you have a Full Backup of all your data first. But this time I would not provide that warning myself, because this Should go smoothly without problems unless the problem was deeper than that, or the disks used special formatting, or you had an odd layout going or they are odd disk types.

Usually if a person had formatted (and preferably tested) the disks fully in the system , or partitioned them and all, they would have a new ID from the system. I assume in this situation the manufactured items were just applied, and all manufactured the same way ?

Yes using completly different brands they are way less likly to have this issue.