it's userscript for greasemonkey(for firefox)-- just google greasemonkey, and then install that, then look for the video download script. it's pretty easy to figure out. Then when you go to YT or Google video, a bar will appear asking if you want the dl link, click and save as whaeveryouredownloading.flv(make sure to add that. then you can convert it to something playable(or if you have something that will play .flv(such as Kmplayer)). I like SUPER video converter.