Thanks for help people like me

I'm using linuxmint 7 and my problem is that every time I go to Nvidia X server settings this box appear:
You do not appear to be using the NVIDIA X driver. Please edit your X configuration file (just run `nvidia-xconfig` as root), and restart the X server.
....and of course I don't know how to do this... so someone can be gentle and tell me what to do?

Thanx, AstridH