the replay file uses the game to play its not actually a video file. It is just a series of commands the games then plays back.
how to record replays in video format:
things you will need
1. screen recorder (ie:fraps,camstudio(Free),playclaw, Bandicam, etc...)
2. coh2
3. the replay file
first, boot up your chosen screen recorder whether it be fraps or whatever.
second, boot up coh2 and access and go to replays (it at the bottom of main menu.)
third, play the replay (the game should start loading kinda like a regular game except you will be the only player loading. this might be a good time to start up your screen recorder.
fourth, the game will start and you can free roam the battle field and see whats going on. allowing you to get all those sexy angles you didnt' have time to get in game.

(when your done make sure you turn off the recorder ive racked up alot of gigs on accident doing that.)
fifth, upload the video (edit it whatever.)
note: using a screen recorder can slow down your computer heavily(may not be able to use max settings) and the video files take up alot of hardisk space so make sure you have some to spare. (these are especially true with fraps.)