MKV to XviD

I want to convert MKV files to High Quality XviD avi files. How can I do it? What tools do i need? Can anyone please describe me?

Did you try this first?
http://clusty.com/search?query=MKV+t...Mozilla-search

Yes I have seen this. But I am telling that which tools are the best? Like for DVD to Xvid we have AutoGK perhaps the best one. Like this do we have such a software or not for MKV to Xvid?