Windows Media Player, VideoLAN, and Quicktime all causing the computer to choke

Hello,
I am experiencing problems trying to open and play videos and trailers. Whenever I do this, 99 or 100 percent of the CPU is somehow diverted to that program which is running the video and nothing plays. If I’m lucky, one second of sound will play, but never the visual. Also, videos I could previously play before I reformatted, can now not play.
Thanks