After upgrading to a new graphics card, Windows Update wants to install a new driver for my former card.
I was using an AMD Radeon HD 7670 and I switched to an Nvidia GTX 750 Ti.
I'm running Windows 8.1.
You didn't mention your OS or the models of the cards you swapped.
If you upgraded for example a relatively recent nvidia card to a newer nvidia card, there's a chance they use the same drivers. And this would mean that windows simply updates the drivers you need but didn't change the name appropriately. If you changed your nvidia for an amd radeon card for example, this shouldn't happen.
However, it is always recommended to completely uninstall all software and drivers from the old graphics card before updating to a new one. Then install the most recent drivers downloaded from your cards site.
Edit your answer to include the model of the cards themselves, and we might be able to provide more specific information.
Check "Device Manager", and use the menu item 'show hidden devices'. If the driver wasn't properly uninstalled it will appear in the list next to the Nvidia card. You can 'uninstall' it by using the right click menu.
Also be careful, you don't say what motherboard/cpu you have, it might be if you have an AMD motherboard with onboard graphics, Windows is installing the driver for that.