What game are you playing?
In the meantime please try to update the Intel® HD Graphics driver , download the zip version and follow these steps;
1. Login with administrator privileges
2. Open Control Panel
3. Open Device Manager
4. Click on "Display adapters"
5. Double click "Intel HD Graphics"
6. Click on the "Driver" tab
7. Click on "Update Driver" button
8. Click on "Browse my computer for driver software"
9. Click on "Let me pick from a list of device drivers on my computer"
10. Click on "Have Disk" button
11. Click "Browse"
12. Navigate to the folder that you unzipped the Intel HD Graphics driver to
13. Navigate to the Graphics sub-folder
14. Double click the igdlh64.inf or igdlh.inf file <-- depends on if you have 32 or 64 bit OS
15. Click "OK"
16. Click "Next", Driver should now be installing.
17. If successful, click "Close", Reboot.
I'm playing Maplestory. I tried talking to their customer support but so far they haven't been able to come up with any options. I followed your directions but was stopped at step 5. The only display adapter showing is my graphics card driver. Intel HD Graphics wasn't in there.
Bear in mind that whenever you add a graphics card to the motherboard it will disable the graphics provided by the processor unless you have a feature in the BIOS that can provide you to choose between them. That is the reason why you are not able to see the Intel® HD Graphics 4600 on the device manager when the graphics card is plugged on the motherboard. Try removing the video card and test if the issue still persists.
For further reference Multiple Displays Frequently Asked Questions (FAQ) for Graphics...