1.> You need Google Video Player to play the videos downloaded from Google. You can download the Google Video Player along with many other useful software from Google using the Google Pack Download link [Click here].
2.> Click on the "Download Video" link found on the right hand side of any Google Video - when using the Google Video Player.
3.>If you donot have the free Google Video Player, please download it from this link before you proceed to the next step.
4.> All the videos would be downloaded to your "My Documents \ My Videos " folder.
5.> Once the whole movie is downloaded, you can watch it from the small file you downloaded to your desktop or from your "My Documents\My Videos" folder.