Reboot the system and at the first post screen tap the Del key normally and it should get you into the BIOS
In there find either the Advanced, Onboard or Integrated Peripherals areas.
Using the keyboard arrow keys scroll down to the Video entry and make sure it is Dis-Enabled and if not then look at the bottom of the screen it will tell you how to adjust or modify the values to Enable it.
When done make sure to click F10 to Save and Exit with the setting.
You will then be asked to click Y to Verify the Save and Exit
The system will now reboot with the new settings saved.
Let me know if this helps.