(If using Windows 10,) Windows 10 has a "feature" whereby it's own update servers will install their own drivers (as tested) on your computer based on your hardware, regardless of how you have or intend to have the hardware configured. I just spent a number of mind-bending days dealing with this and Windows overwriting the driver for and thus breaking one of my (older) graphics cards, that requires a special modified .inf file to install. Days.
Go here for the fix. There are two ways to do it, driven by your version of Windows 10, Pro or Home. One fix involves the Group Policy Editor (Win 10 Pro only), and the other involves the Registry Editor (Win 10 Pro or Home). Be very careful and follow the instructions to the letter, or download and run their patch.