Sorry to break it too you, but there are not too many free programs that will convert one format to another (especially Real Media).
I got sick and tired of looking for one that I finally went and paid for one (Xilisoft Video Converter:Convert video AVI MPEG WMV MP4 MKV converter). I primarily use it to convert video files for use on my iPod touch (2nd Gen 32gig)
As for your disc read errors, as soon as you said that the dvd burns at 16x I knew what your problem was: The DVDs that you're using cannot be used at 24x. In the future, if your burning program defaults to a slower speed then what your drive is capable of, leave that setting alone, since its the max speed that the DvD can be burned at.
My suggestion is to A) Not use Real Media. No subbing group in their right minds uses that format anymore, and its proprietory. B) if you're burning Data dvds for playing on divx capable dvd players, stick to xvid and divx formats (most, if not all videos that have the .avi extention are encoded with either of those too codecs anyways)
Moving to Tech Center. Please remember that the Feedback and Questions area is just for Forum related issues.