First make sure the DVI is plugged into the graphics card and not the motherboard (done in your case). I am generalizing this answer so anyone with similar issues can solve this. If you are on a PC, you might not have all of these options available to you. You should still go through all of them and find what works best for you.
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For Laptops:
The dedicated GPU and onboard GPU should always be enabled. I suggest you install the Intel(R) HD Graphics driver back from your manufacturers website. Do not disable your Intel GPU.
Nvidia Optimus (laptops) switches from integrated graphics (saves power) to dedicated graphics when it needs to.
Try to run your computer in "Maximum Performance" under windows power settings.
If you uninstall/disable your integrated graphics it'll change from "Intel HD xxxx" to "Microsoft Basic VGA Adapter" and more than likely turn your monitor off.
Go into your Nvidia Control Panel > Manage 3D Settings > Global Settings > Select to use High Performance Processor/Nvidia card
If you tried that and it doesn't work, set the individual program (ie. warhammer) to launch with it in the programs list ("Program Settings" directly beside "Global Settings")
This will force games to launch using the Nvidia GPU.
Now for PCs and if the above doesn't work for laptop users:
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Go to surround, PhysX and make sure GTX 980 is selected.
If that still doesn't work, go into the BIOS and do the following:
Disable the on-board graphics, possibly by disabling any shared graphics memory (or setting allocation to automatic).
Or
Set the primary adapter to be the dedicated card, PCI-e x16 or similar (BIOS dependent).
In some cases (mostly laptops) right-click on the game icon and click "Run with graphics processor". You could choose from the options as "integrated graphics" and "High performance Nvidia Graphics".
Cheers