If you install or update a lot of software and developer SDKs on your computer, pretty soon you end up with duplicate path values in your environment variables, especially for PATH. Recent versions of Rapid Environment Editor (a must-have tool) have a cleanup feature that makes removing these duplicates easy. Right-click on any environment variable and you will find Cleanup paths there in the menu. This removes empty and duplicate path values from the variable.
Tried with: Rapid Environment Editor 6.1 Build 794