There are numerous ways, man. I use video-card acceleration, by using MPC-HC:
http://www.xvidvideo.ru/media-player-classic-home-cinema-x86-x64/
If your video card supports DXVA, you should use that. If not, you should use ffdshow+mpc+haali media splitter.
What video card, CPU do you have and what OS are you using?