In order to download and covert videos from YouTube, Google Videos, Metcafe, etc you will have to download Free FLV convertor. Install it. On the interface of FLV convertor you will see the button "Search Videos", type the video name and search for it. Then put a check mark near the videos that you would like to download and then click on the Tube downloader button, here you will see the videos that you have selected being download, once download it automatically converts into the desired format such as .avi, ipod, iphon or 3gp. On the Tube downloader interface you put the target location and other specification such as video quality.
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Just go to http://keepvid.com/. and paste the URL of the video you want and click download. Then below you will get an option asking the format in which you want to download viz. .flv or .mp4...as simple as that.