MKV to AVI Converter?

Hi, guys, convert MKV file to AVI file, that's easy, but I don't think there is a free converter can do that well, because I have tried many free softwares, none of them work well, some of them have many limits, some of them are poor quality, some of them are so slow, some of them even have virus, so now I'm using a cheap software RZ Video Converter to do that, it can convert any video files or audio files between different formats, such as convert MKV file to AVI file, etc, you can yahoo or google search and download RZ Video Converter, only register version without watermark, but so cheap, hope it can help you.