Accessing secondary display adapter without running it.

Basic issue, haven't seen any resolutions out there so I figured I'd go to the source. I am running an Alienware 17 with a AMD HD8970 and an AMD Radeon R9 290X. Here's the issue, the 8970 works fine but unfortunately, the 290 is running on a corrupted driver. This is easy to fix as it would mean just downloading a fresh driver but I cannot do this while the 290 is running as it is completely unusable (heavy flickering, almost looks like a damaged LCD but the LCD is fine). 

So, I know this makes me sound like a bit of a scrub but how can I download a driver for a display adapter that, as far as the device manager is concerned, is nonexistent as long as it's not the primary card?

Just to clarify, I am not asking how to change display adapters, install an adapter, or how to update a primary adapter. I need to update a secondary adapter while the primary is still running. Really hoping I don't have to run this through the bios but if it can't be helped, a quick tutorial would be awesome as I haven't had to edit a bios since 2005.