I use nero to play what is defined in filename as HDTV.xvid. This usually only means that the source that it was converted to xvid from was HDTV. You should try checking the file. I use afreeCodecVT http://afreecodec.com/
but there are many others out there

I use mPlayer for files I can't play with any other apps or where the sounds out of sync
you can put movie in sync with it