Throw those dm_84 files into your et folder under the demo directory(eg. c:/enemyterritory/etpub/demo/)
Then run game, select etpub mod and in options click replay and a window should pop-up with the demo files to watch.

Thanks Nelots , have worked it out , thanks very much,Cheers Boges

If you don’t want to have to go into et to play them, then you can download seismovision for free which will play the vids.