Make the path in raw string, add 'r':
driver = webdriver.PhantomJS(executable_path=r'D:\Python\phantomjs-2.0.0-windows\bin\phantomjs.exe')
For simplicity's sake place the executable in the same directory as your script:
driver = webdriver.PhantomJS() # now there's no need for a path
For me none of the above solved the problem; I found the code:
driver = webdriver.PhantomJS()
Will only work for root...