every single soundchip ive known has loudness equalization built into their drivers. go to your soundcards control panel and find the option. even if you dont have the full driver package installed, go to control panel, sound, right click on your speakers, properties, enhancements, and click on "loudness equalization".
it works wonders for tv and movies, but i warn you it makes music sound bad. i too have to use it for tv and movies though, the volume changes are ridiculous sometimes.