java - Selenium Web driver exception "Unable to find executable for: taskkill " -

when run (driver.quit), opens firefox browser , quit expected error given "unable find executable for: taskkill".
set environment variable path "c:\windows\system32" , run test. still getting error.

i using selenium-java-2.48.2.jar , firefox 42.0

public void closebrowser(){         try{                         driver.quit();                   }         catch(exception ex){             system.out.println(ex.getmessage());         }     } 

i suggest use driver.close() instead driver.quit(). understnad difference between them please see question.