Good guide, though a much easier way would be to just use Avidemux (Direct cutting with preview, no source reencoding required), or use fcchandler's input plugins (mastroska plugin in this case) for VirtualDub (Direct cutting with preview, lots of editing options & much more precise cutting compared to Avidemux, though reecoding of source is required)
http://fixounet.free.fr/avidemux/download.html
http://gral.y0.pl/~fcchandler/