Turns out that Google Video’s downloads, called .gvi files, are just standard .avi files that have been altered to be unplayable in Windows Media Player. When you click in Google Video to download a video to Windows/Mac, you download a .gvp bookmark, which loads Google Video Player and downloads the appropriate .gvi file (opening the .gvp in a text editor will reveal the URL of the .gvi, if you don’t want to install the Video Player).Check it out over InsideGoogle.
Howto play Google videos in Windows Media Player
Posted on Monday, September 25 2006 @ 6:22 CEST by Thomas De Maesschalck