For my laptop I have an external hard disk and a DVD drive which is in the docking station.

With the disk management I clearly set the letter D for the external harddrive and E for the DVD drive.

However, sometimes this still gets swapped and I need to use the disk manager to change back the letters by hand. That's quite frustrating, specifically since programs are relying on constant drive letters.

Why are the drive letters not as constant as they should be and how can this be prevented?

My guess is the connection order; when the DVD drive is connected slighly earlier and D is free it will use D instead of E. When the disk drive is connected D is already taken and assigned to E. But D should never be taken except for this one drive. And E should never be taken except for the DVD drive!

  • Are you using the SAME usb port(physical slot) when you connecting external HDD ?
    – Alex
    Jan 25, 2017 at 5:21
  • The "external HDD" is actually a VHD file on an internal SD card which is mounted to the junction "c:\SD Card". So yes, it is ALWAYS the same "physical" interface. Also the CD drive is docking station so hence should be the same physical interface.
    – divB
    Jan 25, 2017 at 18:29
  • Are you connecting anything after the disconnect these DVD/HDD to your laptop? Did you tried assigning some higher drive letters to those things?
    – Hex
    Jan 26, 2017 at 19:11

1 Answer 1


With windows all external drive letters are freed when you unmount them so another external usb device can easily reuse those letters. So every time you remove(unmount) your external drive it will loose the drive letter you assigned.

you can see this post for a workaround https://superuser.com/a/38367/653717

Edit: the assignment will be done in the alphabetical order

  • Not in my experience, if i set some odd (like X:) letter to pendrive, it's assigned every time when i connect it (only on that PC)
    – Hex
    Jan 26, 2017 at 18:28
  • @Hex the op experience seems better than yours check the thread added and the link to USBDLM it's stated there "You can change the letter assignments in the Windows Disk Management Console with a lot of mouse clicks but you have to do it again for every new device. " and the op is trying to set letter D as he said Jan 26, 2017 at 18:37
  • so try setting letter D and test your experience again you will see you are completly wrong Jan 26, 2017 at 18:47
  • just did the test myself right now on windows 8 . If you assign letters close to D you will surely loose them very quickly when a new drive will be connected Jan 26, 2017 at 18:55
  • Lowest i could was I: and J:, both kept their assignments, no matter what connection order.
    – Hex
    Jan 26, 2017 at 18:57

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