[Carlos Silva] "Considering the use this kind of video (with white background), how to remove the background inside Vegas (using Vegas tools)? The idea is use the animated chart above other background. Is it related to chroma key? Considering it possible, could I use the same to WMV or AVI formats?"
Yes, you would need to use the Chroma Key tool to key out the white background and make sure that you don't use white anywhere in your animation. Uncompressed AVI files would work better than WMV because WMV is so highly compressed you might not get a clean key.
~jr
http://www.johnrofrano.com
http://www.vasst.com 
