I'm sure Willow will be along in the morning to give you some thoughts about how to manipulate this, but a couple of thoughts...
1. Do you have the most current drivers for your video card? Or is that where you're getting stuck?
2. Have you done the virtualdub thing, so that the video files are uncompressed? If they're not compressed, you may not need the codec (which stands for "compression/decompression", IIRC, just like "modem").
3. Have you done the rest of the WinXP tweaks for W&W? Check the Tech Tips thread above to make sure you're covered.
4. Have you done a google search? I came across
this link from Microsoft Support which has a resolution for free.