DivX.it

Ho virtualdubmod
ma non riesco a convertire i miei files mkv in avi
li carico e mi da questo messaggio:
MKV: The video may have a variable framerate,if so we strongly
advise you to use another tool to safely process your file.

Couldn't locate decompressor for format 'yyyyy'(unknow)
virtualdub requires a video for windows (vfw)
compatible codec to decompress video.
DirectShow codec, such as those used by windows media player
are not suitable. Only "direct stream copy" is avaiable for this video.

Io non sò assolutamente che fare qualcuno può darmi una mano?
grazie