Watching most web videos, like those on YouTube, is basically like watching a show on TV. There is no direct way to record what you are watching from within your web browser (Firefox). You have to download the video and save it to your hard drive first, then, if you have the right software program, you can save it or burn it to your CD or DVD writer. You are using Windows XP, which does not include the capability to burn video CDs or DVDs. You have to get a software program designed for this and install it, unless your computer came with a program to do this. A Google search for "DVD burning software Windows XP" should get you lots of choices. Most of the popular web video sites are not set up to allow users to download or copy their video content, because of copyright restrictions or website traffic and advertising considerations. There are some programs available that allow you to download or capture content from these sites, but using them is generally a violation of the terms of service for these sites. Your question was rather general, so if there is a particular type of video file or a particular site you are interested in, you may want to update your question with more specific information.