If I plug an external drive into a system, and it has the same letter assigned as an internal one, which one changes?

Malachite Dragon 0 Reputation points

The title pretty much sums it up; I intend to bring the SSD over from my old computer into the new one that I've just build to use as a backup drive, but it served as the boot drive for that computer and both it and the boot drive of the current computer are both assigned the letter C. I know that if Windows has two drives with the same letter it will force one of them to change- My question is will the one that's forced to change be the second one plugged in (the external drive), or the internal one (the new boot drive) which with my luck will probably break something? Or is it selected at random and I would have to roll the dice?

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  1. Darrell Gorter 1,471 Reputation points

    The drive letter information is stored in the Windows Registry not with the drive itself.

    The Drive GUID is assigned a drive letter which is stored at HKLM\System\Mounted Devices.

    So the new Windows machine has no knowledge of the drive letter from the old machine, it should examine the Drie GUID and assign it the next available drive letter.

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  2. Wesley Li 6,760 Reputation points


    When you connect two drives with the same letter to a Windows system, Windows will automatically assign a different drive letter to one of the drives to resolve the conflict. Generally, the drive that is forced to change is the one that is recognized last by the system. In your case, if you plug in the SSD that was previously the boot drive after the new system is up and running, it is likely that the SSD will be the one to receive a new drive letter.


    To avoid any issues, you can manually change the drive letter of the old SSD before connecting it to the new computer. You can do this by going to Disk Management in Windows, right-clicking on the drive, and selecting 'Change Drive Letter and Paths'. From there, you can assign a new letter that doesn't conflict with any other drives in your system.


    It's also worth noting that if you have any programs or references that rely on the old SSD's drive letter, you may need to update those references to the new drive letter to ensure everything works correctly.

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