How to create virtual disks

Let's say you have a veeeeeeeeeeeeery big path for a file to find and you don't remember the path. You should first have created a virtual disk with this path. How to create one? The code is here.
1. Open Notepad.
2. Write the code:
@echo off
subst x: "%systemroot%"
3. Save as virtual_disk.bat
I explained @echo off before, so now I'll explain only the second line.
subst x: =This creates a virtual disk in the selected letter, where x is the letter.
"xxxx"=This shows the path to be associated where xxx is the path. (%systemroot% means the Winows path).