Updating Display driver?

I'm trying to update the drivers on my NVIDIA GeForce 8600 GT from version
156.64 to 164.75. But everytime I go to install it, it says the operating
system in use is not Windows Vista 32 bit. I DO have Vista 32 bit, I even
tried installing the 64 bit one, and it says the same thing when I do that
too. So I basically can't update my drivers because it doesn't want to
recognize my OS. Anyone know why this is?