Im assuming you have fraps installed. Go to the film capturing part and change the hotkey for recording to something that has NO FUNCTION in film viewer (I use the "R" key). Then uncheck the racord sounds, it is poor qualitly and will make the avis unneccessarily large.
Now close ALL PROGRAMS running in the background. Then open both FRAPS and Film viever (If you want to you can go and change vid settings/anti aliasing in AH game first - for higher quality films, but thats not neccessary).
Open the film you want, play it back at the settings, angle, POV, distance etc you want to - hit your hotkey to record. FRAPS will dump the recorded avis in the folder you designated first. The bigger your window was, the higher res the avi will be (best is to maximize Vievwer for recording).
Now you can play back those avis in the Media Player. But you can also import them into some editing software (like Movie Maker or Sony Vegas) and add sounds, music, effects etc.