How do I actually USE the pixel shader and vertex shader on my Nvidia Geforce FX 5500. (Driver problem?)?

I've read around that my card supports Pixel Shader 2.0 and Vertex Shader 2.0, but I was recently playing Portal and happened to open the console and it said it couldn't load pixel shader. I open the Nvidia control panel, and low and behold, I'm don't even see it in there. I think I need some forceware drivers, but I don't know what the most recent version is that supports my card... On dialup or I'd look more...