I have been asked this question so many times that I thought I might as well post a proper screenshot with all the steps (starting with the “Start” button) for how to get to your system environment variables in Windows. I used Windows 7, but intentionally followed similar steps to those I have followed in other Windows environments like XP and Vista:
A quicker way to do this in Windows 7 specifically is to simply begin typing “environment variables” in the Start > Search bar as shown below: