I have some virtual Windows-7 machines, referring to a D:-drive. This D:-drive seems to be configured as a drive mapping, as can be seen in the result of the subst command:

D:\: => C:\d_drive

I have a copy of this machine, where I'd like to map the same drive, but this seems not to work:

Prompt>subst D: C:\d_drive
Invalid parameter - D:

For your information:

  1. The command subst does not mention the D:-drive already being mapped.
  2. The command net use does not mention the D:-drive already being used.
  3. Configuration settings, Computer management, Disk management does not mention the D:-drive already existing.
  4. I don't see anything in the event viewer (or I'm looking at the wrong place).

What might be going wrong here? What might cause subst to refuse to map this D:-drive?

  • If you run wmic logicaldisk get name as the same user, i.e. same command prompt as the failing subst command, does D: appear? – HelpingHand Mar 3 '17 at 13:39
  • Yes, indeed, D:-drive is one of the mentioned names. What does this mean? – Dominique Mar 6 '17 at 14:48
  • D:-drive seems to be the CD-ROM disk. As I'm working here with a virtual machine, I don't need this and I'd like to remove it, but the command wmic logicaldisk D: DELETE seems not to work (Provider is not capable of the attempted operation), even not when logged as administrator. What now? – Dominique Mar 6 '17 at 14:58
  • Could it be virtual? Maybe even a disk image file. I would check the CD-ROM settings for the VM. – HelpingHand Mar 6 '17 at 18:36
  • Meanwhile I found the solution: using computer management, I modified the drive letter of the CD-ROM, and as a result, D:-drive became available for drive mapping. @EMK: your comment was the first step towards the final solution. Please rephrase it as an answer, so that I can accept it. – Dominique Mar 7 '17 at 8:03

If you get the following error message when running subst:

Invalid parameter

I would suggest initially checking if the drive you are referencing is already in use by the system. To check, in the same command prompt as the one you you are running subst run the command:

 wmic logicaldisk get name

The output of this will be something like:


Note: For a drive that is already created with subst you will get the error:

Drive already SUBSTed


Try something like R instead of D. Maybe D is reserved for a CD drive.

C:\Users\user>subst R: c:\crp

^^^ that worked

The device is not ready.

^^ looks like D is used already

The system cannot find the drive specified.

^^^ that's the [normal] message when a drive letter isn't assigned 

C:\Users\user>subst D: c:\crp
Invalid parameter - D:

^^^ see I get the same error as you when I try it with D. Try it with R.


The short answer is D: already exists. Try something like subst C: F:\temo and you get the "Invalid Parameter - C:". Can't do it because it already exists and hence the error.

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