It's simple. You have to open the control panel, select the icon that uninstalls the window programs and then remove the NVIDIA drivers. But before you do it make sure that you have downloaded the new drivers from the NVIDIA site. As an alternative option you could download DDU and remove the old drivers form there. Finally shut down your system, remove the old GPU, put the new one in, power your system, log into windows and install the new drivers you previously downloaded. If you don't have much experience you could also watch a tutorial in you tube. There are plenty available. Good luck.