if you dont have any video editing software, just use windows movie maker..
1) import the avi file into the project.
2) play the video
3) pause at where you'd like to capture the image from
4) press the camera button on the player on the bottom left.
5) woahla! u got urself an image capture.
if ur using adobe premiere,
1) scroll to where you want to capture the frame at
2) go to file > export > frame
3) woahla !