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Windows 7: Changing External Hard Drive Letter

06 Sep 2011   #1
RP McIntosh

Windows 7 Ultimate 64
 
 
Changing External Hard Drive Letter

I have a situation that isn't really a major problem, but is slightly annoying, and somewhat puzzling.

I have an external 1TB Iomega USB hard drive on my system. It is set to be Drive Y. Most of the time, everything is fine. But occasionally, after I boot the system, I'll get the pop up on the screen asking me what I want to do with Drive J. And yes, the "new" Drive J is, indeed, really my Iomega external drive. I can go into Disk Management, and reassign the drive letter back to Y, and everything is fine again.

Sometimes, it keeps the Y drive letter for several months at a time. But other times, the system treats it as a new drive and assigns drive letter J to it--in anywhere from a few days to several months after the previous time.

As I said, it doesn't happen often enough to be a problem, but I'm curious as to what causes it. Anyone have any insights into this little puzzle?


My System SpecsSystem Spec
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06 Sep 2011   #2
fjawodfc

Windows 7 Professional x64
 
 

Look in your registry under HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices. That's where drive letter assignments are stored. Find \DosDevices\Y: on the left side and note the data value on the right. The next time it happens, check the same registry location but find \DosDevices\J: and see if the data value is the same as before. Also see if there's still an entry for \DosDevices\Y:.

(Option Two)
http://www.sevenforums.com/tutorials...ndows-7-a.html

-mounteddevices.png


My System SpecsSystem Spec
07 Sep 2011   #3
RP McIntosh

Windows 7 Ultimate 64
 
 

Quote   Quote: Originally Posted by fjawodfc View Post
Look in your registry under HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices. That's where drive letter assignments are stored. Find \DosDevices\Y: on the left side and note the data value on the right. The next time it happens, check the same registry location but find \DosDevices\J: and see if the data value is the same as before. Also see if there's still an entry for \DosDevices\Y:.

(Option Two)
http://www.sevenforums.com/tutorials...ndows-7-a.html

Attachment 174151
Thanks. I've exported that registry key to a text file, so that the next time it happens, I can compare the entries as you suggest. I'll let you know what happens, though it may be some time before I get the behavior again.

I'm guessing that there will NOT still be an entry for \DosDevices\Y: only because when I go to Disk Management to change the drive letter, Y is always available as a drive letter. I'm guessing that if there were an entry for it in the key, the drive letter would not be available in Disk Management.
My System SpecsSystem Spec
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07 Sep 2011   #4
Britton30
Microsoft MVP

Windows 7 Ultimate X64 SP1
 
 

RP I think you've stumbled on one of Windows 7's annoying quirks. It will assign drive letters as it darn well pleases at times. So far no one has a solution for it but really causes no harm.
My System SpecsSystem Spec
07 Sep 2011   #5
marsmimar

Microsoft Community Contributor Award Recipient

 
 

These are just some random thoughts so please forgive me if it sounds weird. Also, my usual disclaimer: I'm not an expert in anything.

Instead of leaving the external drive as just (Y: ) what would happen if you renamed it to something else? Like "Data Backup (Y: )".

Drive - Rename

Another thought is perhaps one of your system files got damaged or corrupt in some way. You could try running a System File Checker scan. It will check the integrity of all protected Windows 7 system files and replace incorrect, corrupted, changed, or damaged versions with the correct versions if possible.

SFC /SCANNOW Command - System File Checker

And a final thought is if you have any other removable USB devices like a flash drive, camera, scanner, etc. If the Iomega external drive is unplugged (or if it has a separate power switch that gets turned off) and another device is plugged in, it might be assigned Drive Y: because that's a known assigned drive letter that's been previously used. Then when you plug in or turn on the Iomega it may get assigned J: because for whatever the reason, it's also a known drive letter that's been previously used. (I don't think Windows 7 or the computer will make a distinction between a HD, Flash drive, camera, etc. But I could be wrong.)

Anyway, just my two cents worth.
My System SpecsSystem Spec
07 Sep 2011   #6
Bill2

Windows 7 x64 pro/ Windows 7 x86 Pro/ XP SP3 x86
 
 

Thats the way windows will work. But you can try USBDLM.

USB Drive Letter Manager - USBDLM
My System SpecsSystem Spec
08 Sep 2011   #7
RP McIntosh

Windows 7 Ultimate 64
 
 

Quote   Quote: Originally Posted by Britton30 View Post
RP I think you've stumbled on one of Windows 7's annoying quirks. It will assign drive letters as it darn well pleases at times. So far no one has a solution for it but really causes no harm.

Thanks. I agree it's a minor annoyance. But I feel better finding out that it is something that others experience too, and not some more serious problem with my system.
My System SpecsSystem Spec
08 Sep 2011   #8
RP McIntosh

Windows 7 Ultimate 64
 
 

Quote   Quote: Originally Posted by marsmimar View Post
These are just some random thoughts so please forgive me if it sounds weird. Also, my usual disclaimer: I'm not an expert in anything.

Instead of leaving the external drive as just (Y: ) what would happen if you renamed it to something else? Like "Data Backup (Y: )".

Drive - Rename

Another thought is perhaps one of your system files got damaged or corrupt in some way. You could try running a System File Checker scan. It will check the integrity of all protected Windows 7 system files and replace incorrect, corrupted, changed, or damaged versions with the correct versions if possible.

SFC /SCANNOW Command - System File Checker

And a final thought is if you have any other removable USB devices like a flash drive, camera, scanner, etc. If the Iomega external drive is unplugged (or if it has a separate power switch that gets turned off) and another device is plugged in, it might be assigned Drive Y: because that's a known assigned drive letter that's been previously used. Then when you plug in or turn on the Iomega it may get assigned J: because for whatever the reason, it's also a known drive letter that's been previously used. (I don't think Windows 7 or the computer will make a distinction between a HD, Flash drive, camera, etc. But I could be wrong.)

Anyway, just my two cents worth.
Thanks for the comments. Actually, it has a name (IOMEGA_HDD) which I assume is the default that Iomega gave it. And I have run the SFC and it comes up clean. The only other USB device I have is a card reader (which registers as 4 drives when connected). But I only connect it when I want to use it. Windows always assigns it drive letters J, K, L, and M. And that's fine with me. I originally put the Iomega drive to Y so that if I used other devices, the drive letter wouldn't be affected, since I use it for backup, and my backup software is configured to backup to predetermined drives and folders. But apparently, it is a quirk of Windows, so I'll just live with it.
My System SpecsSystem Spec
08 Sep 2011   #9
RP McIntosh

Windows 7 Ultimate 64
 
 

Quote   Quote: Originally Posted by Bill2 View Post
Thats the way windows will work. But you can try USBDLM.

USB Drive Letter Manager - USBDLM

Thanks. Now that I know it is just a quirk, I can just live with it. But thanks for the info on USBDLM.
My System SpecsSystem Spec
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