I have WinAvi video converter(latest version) I use it to convert MKV,MP4, etc... to AVI?

I convert the files to put them on a flash for use in a divx capable dvd player after converting to avi the DVD player recognizes the files but will not play them any help or recommendations for a better converter I tried Xillisoft, Magic, and IMTOO all ending with same result.Files aren't damaged and play flawlessly on PC???