How to map a drive letter to a local Windows folder

We freelancers are using Dropbox as a virtual network for our civil engineering and AutoCAD Civil 3D files. And it's really great (especially since I have a daily backup set up).  But some programs want us all to have the same absolute path to our files.  To do that, we have to each map our Dropbox folder to the same virtual drive letter.  Piece of cake!

Temporary

First map the drive letter temporarily so you see it works.  Click the Windows Start button (in the lower left corner), then Run... or if you are in Windows 8/10+, just type into the Cortana/Search box.

subst T: "C:\Users\my user name\Dropbox"


You should see the new drive appear in your File Explorer.  And you should be able to browse to it and refer to it like a drive in all your programs.

Permanent

Next map the drive letter permanently in the Windows Registry.  Click the Windows Start button (in the lower left corner), then Run... or if you are in Windows 8/10+, just type into the Cortana/Search box.

regedit 

In the regedit window, browse to the location below and Add a string value as shown:

Browse in regedit to
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run