try getting ac3 filter. and dont install any codecs till you know u dont have the problems with winxp, mpegs, or any other things. It might be ur gfx card. I take that its an agp card. Uninstall ur video drivers, and get ur mobos latest chipset drivers( eg ur agp drivers for mobo ) and any other drivers u might want for mobo. Install them, then instal ur latest gfx drivers. Then reinstall ur video drivers, and uninstall all codecs. See if any of this helps