VideoCapture not working in Python (Win 8.1 64 bit)

Question

import cv2
capture = cv2.VideoCapture("slow.avi")
while not capture.isOpened():
  capture = cv2.VideoCapture("slow.avi")
  cv2.waitKey(1000)
  print "Wait for the header"

I tried a lot of different video files(flv,wmv) but I couldn't open any video file.I followed https://stackoverflow.com/a/11703998 directions and copied files in OpenCV\sources\3rdparty\ffmpeg directory to C:\Python27\ directory but not working