Changing video card without formatting pc

Your operating system will recognize your new card
The only thing youll need is the new drivers

To just change a video card does not require formatting the system -- best thing to do is just prior to swapping out the video card with the system running go into the Device manager - go to the video card listing and right click and uninstall the current video card (this will then switch the system to the generic VGA driver) - then shut down the PC - swap out the video cards - reboot and install the new video card using either the CD that came with it or new drivers downloaded from the net.

^+2

You had me up until this. The driver CD should always be ignored(unless perhaps you have no internet connection) as it is undoubtedly outdated.
Also running driver sweeper in between uninstalling the old drivers and installing the new ones is a good idea, especially if you are going from an Nvidia card to ATI or vice versa.
http://www.guru3d.com/category/driversweeper/

All great info for the OP