I was playing games and noticed that they were using the onboard graphics card instead of my NVIDIA 770, so I went into BIOS and disabled what I believe was an Intel Family 4600. I booted up my PC and now it is using the 770 but refuses to recognise that I have a second monitor plugged in. Re-enabling the onboard card fixes the issue, but then I have the same problem I did initally.
If it's any help the second monitor is connected by HDMI
If it's any help the second monitor is connected by HDMI