Import drive letters for use after reinstall?

OAT · Feb 7, 2024

Try3 said:
The OP did not ask about any of that.
You can have batch scripts recognise a volume label and use that to find out the drive's current drive letter for the rest of the script to use. I run such scripts almost every day.
GetDriveLetter-SubRoutine - my post #5 - ElevenForum

Denis

Fair enough, maybe he did not specify the need, but shouldn't that have been mentioned to him?
The fact you need to use a dedicated batch script to recognize the drive because the label alone won't do, proves my point.

Try3 · Feb 7, 2024

OAT said:
proves my point

All I said was

Try3 said:
If you give them each drive labels then they remain constant over time & with different computers.

and you took issue with that

OAT said:
What about batch scripts...
Therefore the drive letter must match the assigned path.

so I explained how to make use of the label in batch scripts. I have not made any other claims.

All the best,
Denis

OAT · Feb 7, 2024

All the best Denis,

OAT

hsehestedt · Feb 7, 2024

There are some apps that will allow you to use the volume label only to reference a drive. The one notable one that comes to mind is "FreeFileSync". It does this specifically to avoid drive letter dependency. It (as well as many other programs) will also allow reference to a drive via the drive GUID rather than a drive letter. Yes, these are exceptions, but they do exist.

However, back to the original topic: If you really, really need to save the drive letters, you could save them from the registry and reimport that on your new install.

CAUTION! - This could be dangerous. I do not suggest doing this, but it should be possible. But, to my thinking, this would be way more work than just assigning the drive letter yourself after installing Windows. For info on where these registry entries are held, see this tutorial:

Change and Assign Drive Letter in Windows 10

How to Change and Assign Drive Letter in Windows 10

www.tenforums.com

Try3 · Feb 7, 2024

I have the same drive used on different computers and I set its drive letter to be the same on them all.
I have always done this manually and thought there was no choice.
Their
HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices
values are the same on two computers e.g.

So H's suggestion might well work.

I'll check my other computers to see if it really is constant.

Denis

SIW2 · Feb 7, 2024

As far as I know a reinstall doesnt alter the volume guids of the non windows volumes. I havent tested, but you could try exporting the current \DosDevices\ from the mounted devices key. Open the reg file and delete the entry for the os letter. Then after the reinstall delete the non os entries from the new mounted dev key and merge the reg file.

Does a DeviceID/GUID for a partition change after Windows reinstall or is it unique/static?

The situation might be different after an image restore - particularly if the whole disk or several volumes are restored.

OAT · Feb 7, 2024

I can see where that would be useful.
But what are the binary values in HEX? Are they pointers to a position on the disk(s) itself?
This is a bit over my head there.

Try3 · Feb 7, 2024

SIW2 said:
you could try exporting the current mounted devices key

I'm now checking-trying.

It works.

Denis

hsehestedt · Feb 7, 2024

SIW2 said:
As far as I know a reinstall doesnt alter the volume guids of the non windows volumes. I havent tested, but you could try exporting the current mounted devices key. Open the reg file and delete the entry for the os letter. Then after the reinstall merge the reg file.

Does a DeviceID/GUID for a partition change after Windows reinstall or is it unique/static? - Microsoft Q&A

Hi. I would like to ask you this, for whoever knows and is kind to help me :) Basically I have created a script that automatically locks a certain BitLocker Volume on demand, without the need for me to restart the PC. Here is a screenshot: You can…

answers.microsoft.com

I do know that the GUID remains the same, so this should work, in theory. But again, I stress caution when mucking with the registry like this

A VM would be a good place to test this. Another advantage of a VM is that you can create a checkpoint and revert back if the world collapses after a registry change.

Another possibility would be to write a script that run a few commands (most likely diskpart commands), parse the output for the GUID and drive letter and save that info, then another script that use that info to assign the same drive letters on the new installation of Windows.

Again, seems like a lot of work for what can be done manually in seconds, but then again, I have often been known to do things the hard way myself

SIW2 · Feb 7, 2024

Doesnt matter as long the os entry is correct. The other dosdevice letter entries can be deleted and windows will generate them on reboot.

Try it for yourself.

hsehestedt · Feb 7, 2024

SIW2 said:
Doesnt matter as long the os entry is correct. The other dosdevice letter entries can be deleted and windows will generate them on reboot.

Try it for yourself.

Good info. Thanks!

Try3 · Feb 7, 2024

I exported the
HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices
key from one computer and deleted all but the drive S entry from the .reg file
Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices]
"\\DosDevices\\S:"=hex:44,4d,49,4f,3a,49,44,3a,6c,97,3a,17,ea,6a,53,46,9d,66,\
aa,ac,5b,33,9b,57

I then imported the .reg onto another computer that had no S drive entry and had never seen the S drive disk.
The S drive entry appeared in the
HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices
key as you'd expect.

I then connected the relevant disk and it was indeed seen as S.

Added later - I have now repeated this procedure for another computer that had no S drive set and had also never seen my S disk. It worked for it as well.
The method works across both Windows 10 & Windows 11.

Spiffing.

Now I'll be able to decide if I want to make use of this method when setting up new computers [next new one due about 2028].
Thanks, Hannes.

Denis

Try3 · Feb 7, 2024

Donk said:
After a new installation, is there a way to automatically assign all external hard drives the drive letters they had in the old installation?

Yes.

See my last post for an example.
You'd have to be comfortable with messing about inside Registry exported .reg files but they are more awkward than difficult.
And you might prefer to create the 'exported' .reg file using reg commands to more quickly arrive at the required result than the manual editing I did for my test.
Reg - SS64
I'd expect the best bet to be writing the individual "\\DosDevices\\S:"= nnnnnnnnnnn
etc entries using Reg Query commands and manipulating the outputs into the syntax needed for importing the results using a Reg Add command.

I only tried this method because of H's post. It had never occurred to me that the entries would be constant across computers let alone that Windows would react obediently to artificially-written entries [this is not always the case].

Denis

Winuser · Feb 7, 2024

Try3 said:
I exported the
HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices
key from one computer and deleted all but the drive S entry from the .reg file
Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices]
"\\DosDevices\\S:"=hex:44,4d,49,4f,3a,49,44,3a,6c,97,3a,17,ea,6a,53,46,9d,66,\
aa,ac,5b,33,9b,57

I then imported the .reg onto another computer that had no S drive entry and had never seen the S drive disk.
The S drive entry appeared in the
HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices
key as you'd expect.

I then connected the relevant disk and it was indeed seen as S.
View attachment 86352

Added later - I have now repeated this procedure for another computer that had no S drive set and had also never seen my S disk. It worked for it as well.
The method works across both Windows 10 & Windows 11.

Spiffing.

Now I'll be able to decide if I want to make use of this method when setting up new computers [next new one due about 2028].
Thanks, Hannes.

Denis

Neat little trick but I'm curious. Is it showing the drive as drive S because it was originally assigned the letter S or would it show whatever the first drive is that got connected as drive S.

Try3 · Feb 7, 2024

Windows has been known to lose drive letters assignments from time to time.
So this method might have a use beyond setting up new computers. It could be used quite routinely to restore configurations.

Try3 · Feb 7, 2024

Winuser said:
Is it showing the drive as drive S because it was originally assigned letter S

It is showing S because that's what the Registry entry tells it to for that piece of hardware.

Winuser said:
would it show whatever the first drive is that got connected as drive S

I have also connected another disk instead and it quite correctly shows its own drive letter not S.
But if my intended S disk was not connected and I happened to connect umpteen other USB drives, Windows would allocate S to one of them when that was the next letter in turn. The intended S would then get assigned whatever letter was next in line if I connected it again whilst the other one was still there.

Denis

Donk · Feb 7, 2024

CAUTION! - This could be dangerous. I do not suggest doing this, but it should be possible. But, to my thinking, this would be way more work than just assigning the drive letter yourself after installing Windows. For info on where these registry entries are held, see this tutorial:

Many thanks. So one "just" needed to copy that part with the drive letters of the registry and replace the same part of the registry of another Win. That's it? It actually doesn't sound that complicated / complex. But actually I think that maybe it isn't.

As far as I know a reinstall doesnt alter the volume guids of the non windows volumes. I havent tested, but you could try exporting the current \DosDevices\ from the mounted devices key. Open the reg file and delete the entry for the os letter. Then after the reinstall delete the non os entries from the new mounted dev key and merge the reg file.

This is a different approach than the above one?

You'd have to be comfortable with messing about inside Registry exported .reg files but they are more awkward than difficult.

OK, many thanks, I am not at all but perhaps I will try it.

Many thanks!

Try3 · Feb 7, 2024

Try3 said:
You'd have to be comfortable with messing about inside Registry exported .reg files but they are more awkward than difficult.

Donk said:
perhaps I will try it

When you delete the stuff that you are not interested in you have to keep the first line
Windows Registry Editor Version 5.00
and the blank line after that.
You also need to keep the line identifying the Registry Key
[HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices]
and then you can delete everything except those lines that you want that begin
"\\DosDevices\\
So you'll get something in the pattern of my post #32.

Try3 said:
Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices]
"\\DosDevices\\S:"=hex:44,4d,49,4f,3a,49,44,3a,6c,97,3a,17,ea,6a,53,46,9d,66,\
aa,ac,5b,33,9b,57

Denis

Winuser · Feb 7, 2024

Try3 said:
It is showing S because that's what the Registry entry tells it to for that piece of hardware.

I have also connected another disk instead and it quite correctly shows its own drive letter not S.
But if my intended S disk was not connected and I happened to connect umpteen other USB drives, Windows would allocate S to one of them when that was the next letter in turn. The intended S would then get assigned whatever letter was next in line if I connected it again whilst the other one was still there.

Denis

I don't think you fully understood what I was asking or I'm not fully understanding your answer. What I was asking is if you hadn't connected the S drive first would the first drive you connected get it's own drive letter or would it automatically be assigned the drive letter S. I'm not planning on doing anything like that. I was just being curious.

hsehestedt · Feb 7, 2024

Denis, thanks for doing the heavy lifting and doing the initial testing. I'll have to make note of this for "bag of tricks", although I have to admit I'm not really sure if I will ever use it.

Import drive letters for use after reinstall?

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