which program to play .mlk video files

[OpenToSuggestions]

hi, I have a 1080p video file and want to play it on my pc. VLC keeps slowing down (its not a great HD player) and divx says file not supported and media player wont work either.

So what software (preferable free if possible) to play HD content on a pc??
I think my main problem lies witht the file being a .mlk file.

thanks

 

[OpenToSuggestions]

I think you mean .mkv

oops yea i do media player classic?? bit old isnt it?

 

[OpenToSuggestions]

I played 1080p of commando fine, 1080p of the matrix was ok (just).
my pc eats 720p easily

EDIT: i am trying the file in question (band of brothers) whilst WOW is on. guess my cpu isnt good enough for both