Stone Studio

Step 1:

Open your system properties window. Screenshots below are for Windows 7:

Step 2:

Open you Environment Variables Window.

Step 3:

Double Click on you Path (if you want to just change you path for your login, use the top one, if you want to change it for all logins, use the bottom one)

Append the path you would like to add, separated with a semi-colon. Below, I am adding C:\Program Files (x86)\bin

CLI Method

Open a comment window and type

SET PATH=%PATH%;C:\Program Files (x86)\bin

You can type PATH again to see your path variables. Your new path should be added. The problem with this is that this new path variable is only good inside this command window.