I wouldn't know which codec to use, it is not a video file giving trouble but an audio file. I presume most people can play their downloaded files. I am new to Limewire. Previously I had WinMix installed which for some reason or other just stopped working. It was a good program and easy to use and always successful with downloads. Limewire seems very complicated and downloading is a nightmare. I think perhaps I will revert to paying for my tracks from iTunes. Heigh Ho!