.tk file extension

I have downloaded numerous movie files in a .tk file format, but media player keeps telling me that there is an error in downloading the required codec. It will play the audio but no video appears, can anybody help me?

Hi,

i also had a problem whit tk file.
for most of the programs it is a unknown file.
i was trying do burn a downloaded ps2 game (that was a .tk file) but that didnt work i find ou that you have to downloaded a program to change the tk file into a other program.

Matroska and Windows Media Player Classic come to mind.