I assume you're using opengl. If you're not, go to the launcher, hit video, then pick opengl if it says d3d.
If you're using the 3.6.8 vp's, you'll want mv_core, mv_effects, mv_models, mv_textures, and mv_music. I also suggest downloading lightspeed's nebula as they are much better than retail.
However, lighting is not controlled by the .vp's. It's controlled by your flags on the launcher. Look up the flags on the wiki, you can turn down the ambient which makes it look a lot better, and make sure that specular is enabled. There are a lot of other nifty options like fov_ and some specular options whcih you can read about.
If the problem persists, show us a screenie because you were a bit vague about the problem.