SUPER video converter is all around good but you have to read
(Free)
SUPER
AVN Soft Any Video Converter (Free) (not bad but not great)
Any Video Converter at Cnet
I render video all the time and when it comes to freeware, those two are the best; beyond that you need pay software and for those I would recommend Adobe Premier and then Sony Vegas 7 or higher. With either of those you can re-render any HD format to any well known codec. Also be aware that rendering video is literally used for bench marking the performance of PC's so how bad-asssss your PC (CPU & GPU) is, in terms of performance, is going to determine how fast you render, but be ready for some serious wait time know matter what because you are rendering HD video.
gl