With the following 3 steps you can save your youtube and flash videos
Step-1. Open Mozilla or any of your web browser and open web page with the video that you would like to download. Wait until the video loads completely. Eg: YouTube, you can see a lighter red indicator bar reached the right end side.
Step-2. Open /tmp folder (Places-->Computer-->Filesystem-->tmp). Here you can see the flash video that you have just downloaded. The name of the downloaded video file has the word "Flash" on it.
Step-3. Rename the video file with a .flv extension and save it to any folder you like.