What is the make and model of your computer?
Your computer should be able to use generic drivers it already has to run the video card at a basic level. The nVidia drivers should be loaded however to give you increased stability, functionality, and speed.
You can go to the nVidia website and download drivers directly from them. It is easiest if you do this first and store them on a flash drive to load after installing the video card.
You can find detailed, step by step insturctions for installing a video card at this web page, including directions about loading drivers:http://www.upgradevideocards.com/install.html