How do you mount a directory as a drive in Windows 7?

"Use the subst command:
subst X: F:\some\folder
There is also a great freeware paid utility called Visual Subst to make things even easier:

2021 Update: that software is no longer freeware, and now costs 20$. The last free version is 1.0.6, which is still available on download websites such as Softonic and Uptodown."

"Apart from the suggested ways, you could do one more thing. Share the folder and Map as network drive.
Here are the steps:

Step 1: Share the required folder. (You can just share with yourself or Admin group)

a.Right Click on the Folder and select Share with specific people

b.Click Share button on the share with dialog.

c.Copy the share path that is generated.

Step 2: Map the network drive

a.Click on Map Network drive in windows explorer

b.Once it launches, use the previously copied path as the network location.

c.Click on finish and you are done.
Make sure to click on Reconnect on logon.

Benefit is that you get to see the drive grouped separate from other physical drives."