As Fruit Bat /\0/\ says,as it is also an Nvidia card just install the driver over the top of the old one.No need to uninstall anything. The driver that came with your card will not be the latest version,so better to download the newest driver from the Nvidia website.
I would recommend downloading the latest drivers click here first, create a folder on your desktop and save the file in it, then I would uninstall the drivers already on the machine and reboot, it will boot with Windows default drivers and may run at low resolution, perhaps 800x600 that's normal. Shut down the machine, change the card then power on, if the card installation went well then it should reboot to the 800x600 resolution as before, open the folder with the drivers and run the program to install the new drivers.
I've found that through using Revo Uninstaller that NVIDIA drivers uninstall cleanly leaving no errant registry entries and I know this may be a long winded way to do it considering both cards are NVIDIA but I believe it less likely to go wrong doing it this way.
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