I am using selenium with python and have downloaded the chromedriver for my windows computer from this site: http://chromedriver.storage.googleapis.com/index.html?path=2.15/
Could try to restart computer if it doesn't work after you are quite sure that PATH is set correctly.
In my case on windows 7, I always got the error on WebDriverException: Message: for chromedriver, gecodriver, IEDriverServer. I am pretty sure that i have correct path. Restart computer, all work