If you have obtained a .ivf file, then you have an Intel Indeo video technology file. Latest versions of Windows Media Player should play back this video format. Indeo is a video codec that was developed by Intel but now is owned by Ligos . It is often used as in-game video during cutscenes. Media Player Classic is an excellent open source media player that can play back IVF files very well.

Download Media Player Classic from: http://www.afterdawn.com/software/video_software/video_players/media_player_classic.cfm