Hi I have a pensonic sk-5197 with a usb port. It says it can play mp4, mp3, wmp, cd, dvd etc. I was able to play a downloaded movie with an .avi format THROUGH the usb port. So I presumed that videos w/ .avi format are playable in my player. I downloaded another movie w/ an .mkv format and converted it into an .avi format. But my player wouldn't play it, displaying an error message "unsupported file format"...i tried to convert it also w/ .mp4 but i also got the same error...what particular .avi and .mp4 format does this player support??..pls help