How to change drive letters (VBScript)

Hi all,

Imagine you need to map some shared folders to specific drive letters for all users in your domain, so some internal apps your company needs work fine. Imagine your users connected i.e. USB devices to their systems, so the drive letters those apps need are in use when you are going to map them.

The following VBScript sample accepts a list of forbidden drive letters, and it will rename all the drive letters of the system in that list to the next available letter.

Option Explicit


‘ Reserved drives list

Dim arrReservedDrives
arrReservedDrives = Array(“E:”, “F:”, “H:”, “Y:”, “Z:”)

wscript.echo “Reserved drives:”
ShowArray arrReservedDrives


Dim objWMIService, objDrive
Dim colDrives
Dim arrUsedDrives, arrForbiddenDrives
Dim strComputer, strDrive, strNewDrive, strCurrentDrive
Dim i

‘ Get all drives currently in use

strComputer = “.”
Set objWMIService = GetObject(“winmgmts:” _
& “{impersonationLevel=impersonate}!\\” & strComputer & “\root\cimv2”)

Set colDrives = objWMIService.ExecQuery _
(“Select * from Win32_LogicalDisk”)

ReDim arrUsedDrives(colDrives.Count – 1)
i = 0
For Each objDrive in colDrives
arrUsedDrives(i) = objDrive.DeviceID
i = i + 1

wscript.echo “Used drives:”
ShowArray arrUsedDrives

‘ Create a list which contains all drives in use + all reserved drives.
‘ Drives in this list cannot be used at all.
‘ Note I don’t care about duplicated values in this list

arrForbiddenDrives = JoinArrays(arrUsedDrives, arrReservedDrives)

‘ Check each drive currently in use

For Each strDrive in arrUsedDrives
If ArrayContains(arrReservedDrives, strDrive) Then

‘ We found a drive that cannot be used

Wscript.echo strDrive & ” is in use, and it shouldn’t”

‘ Find next available drive

strNewDrive = “”
For i = 68 to 90 ‘ From ‘D’ to ‘Z’
strCurrentDrive = CStr(Chr(i)) & “:”
If (Not ArrayContains(arrForbiddenDrives, strCurrentDrive)) Then
‘ We found it

strNewDrive = strCurrentDrive
Exit For
End If

If strNewDrive = “” Then
‘ There are no more available drives!

Wscript.echo “Error: There are no more available drives in the system!!!!”
Exit For
End If

‘ Change drive that cannot be used to the available drive we found

wscript.echo “Changing ” & strDrive & ” to ” & strNewDrive
ChangeDriveLetterWithMountvol strDrive, strNewDrive

‘ Add the new drive to the list of forbidden drives

AddToArray arrForbiddenDrives, strNewDrive
End If

‘ The end

wscript.echo “We are done!”


‘ Change the drive in one drive letter to another drive letter using
‘ mountvol.exe tool

Sub ChangeDriveLetterWithMountvol(strSourceDrive, strTargetDrive)

Dim objShell, objExec
Dim strVolume

Set objShell = WScript.CreateObject(“WScript.Shell”)

‘ Get volume associated to the old drive letter.

Set objExec = objShell.Exec(“mountvol ” & strSourceDrive & ” /L”)
strVolume = Trim(objExec.StdOut.ReadLine())
while objExec.Status = 0

‘ Unmount the drive.

Set objExec = objShell.Exec(“mountvol ” & strSourceDrive & ” /D”)
while objExec.Status = 0

‘ Mount the drive on the new drive letter.

Set objExec = objShell.Exec(“mountvol ” & strTargetDrive & ” ” & strVolume)
while objExec.Status = 0

End Sub

‘ Join two arrays

Function JoinArrays(arrA, arrB)

Dim i, a, b

ReDim arrNew(UBound(arrA) + UBound(arrB) + 1)

i = 0
For a = 0 to UBound(arrA)
arrNew(i) = arrA(a)
i = i + 1

For b = 0 to UBound(arrB)
arrNew(i) = arrB(b)
i = i + 1

JoinArrays = arrNew

End Function

‘ Looks for a value in an array

Function ArrayContains(arrStrings, strValue)

Dim i

ArrayContains = false
For i = 0 to UBound(arrStrings)
If arrStrings(i) = strValue Then
ArrayContains = true
Exit For
End If

End Function

‘ Adds a value to an array

Function AddToArray(arrStrings, strNewValue)

ReDim Preserve arrStrings(UBound(arrStrings) + 1)
arrStrings(UBound(arrStrings)) = strNewValue
AddToArray = arrStrings

End Function

‘ Shows contents of an array of strings

Sub ShowArray(arrStrings)

Dim str

For Each str in arrStrings
wscript.echo str

End Sub

I hope this helps.



Alex (Alejandro Campos Magencio)

Comments (3)

  1. Jeremias Jansson says:

    EXACTLY what i needed! Tried to script this myself but this is way better. Interesting to see how you solved the problems I had with my script.

    Learned a lot from this, thank you!

  2. Charlie says:

    THANKS! Been looking for a solution this clean for awhile now!

  3. Aaron says:

    This is EXTREMELY helpful!  We had a problem with a Windows 7 sysprep prepared image, that had problems with EJECTED drives if the drive was D.  Only drive D was a problem.  Example is that CD ROM or USB card reader on D, after media ejected, would cause problems with popup "No Disk", "There is no disk in the drive. Please insert a disk into drive D:." Cancel, Try Again, Continue".  With this script, we can REMAP whatever is consuming D to the next available drive letter.  This script has more uses than just reserving for mapped network drives!  THANK YOU!

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