Option 1: Modify the $env:Path Variable

1. Append to the Path variable in the current window:

   $env:Path += ";C:\New directory 1;C:\New directory 2"
   

2. Prefix the Path variable in the current window:

   $env:Path = "C:\New directory 1;C:\New directory 2;" + $env:Path
   

3. Replace the Path variable in the current window (use with caution!):

   $env:Path = "C:\New directory 1;C:\New directory 2"
   

Option 2: Use the editenv Utility

I wrote a Windows command-line tool called editenv that lets you interactively edit the content of an environment variable. It works from a Windows console (notably, it does not work from the PowerShell ISE):

editenv Path

This can be useful when you want to edit and rearrange the directories in your Path in a more interactive fashion, and it affects only the current window.