one thing i typically do to render an animation is pick an encoder along with your movie format. for example advanced render/format/avi movie, then click “options” and under “compressor” tab i get a list of encoders my system has and i pick my “divx” encoder. that’s all it should be. as long as you’ve picked a format,encoder, and the amount of frames to render, and a place to render it, you should not have a problem. hope this helps.