How to mount and unmount hard drives under Windows (the unix way)

Remove the drive letters using mountvol or diskmgmt.msc. Without a drive letter, they won't appear under Computer or Send To.

mountvol Q: /p

Using /p will actually dismount the device. On older Windows versions, you only have /d, which only unassigns the drive letter, but keeps the volume mounted.

Reassign when needed, using the volume ID printed by mountvol:

mountvol Q: \\?\Volume{1be3da43-6602-11e0-b9e6-f11e1c50f5b5}\

You can also mount the volume on an empty folder (Unix style) using the same tools:

mkdir C:\fs\backup-disk
mountvol C:\fs\backup-disk \\?\Volume{1be3da43-6602-11e0-b9e6-f11e1c50f5b5}\

All these operations require Administrator privileges.

(In fact, you might even be able to directly use the volume ID in your backup scripts, without having to mount it anywhere. For example, \\?\Volume{1be3da43-6602-11e0-b9e6-f11e1c50f5b5}\projects instead of Q:\projects.)

Use DISKPART to set your disk offline
It will stay offline even after a restart or a new power on

Use DISKPART to set it back online

This can be done in scripts

command file to put disk 2 offline:


 echo list disk              > c:\windows\temp\namexxxx.none
 echo select disk 2         >> c:\windows\temp\namexxxx.none
 echo offline disk          >> c:\windows\temp\namexxxx.none
 echo exit                  >> c:\windows\temp\namexxxx.none
 diskpart /s c:\windows\temp\namexxxx.none
 erase c:\windows\temp\namexxxx.none

command file to put disk 2 online:


 echo select disk 2 ........
 echo online disk ......

Execute as administrator

The correct answer is using the /P parameter to mountvol (see the comments in the accepted answer to understand why /D is not enough) but that only applies to recent windows versions (NT kernel version 6 and up).

The devcon utility as described in this answer works across all NT versions