Hi Ike Menard
Welcome to Microsoft Community.
Based on your description, I understand that you recently replaced a new motherboard and kept your old graphics card, but recently your computer will be running applications and games using integrated graphics versus a dedicated graphics card, resulting in your CPU casually running at 100%, and I understand very well how you feel!
I'm going to give you some ways to troubleshoot your problem without disabling the integrated graphics card, and hopefully that will solve your problem successfully!
Option 1: Try modifying your Windows power settings to ensure that both your CPU and GPU are set to “Optimal Performance”.
Click “Windows Logo Key” to open the search bar -> Type “Control Panel” -> “Power Option” in the search bar -> Select “High perform”
or some of the power plans ASUS motherboards offer you -> Click “Change plan settings” on the right side and check and modify it.
Option 2: Please try to disable hardware acceleration, because I am a gamer myself, and sometimes hardware acceleration and vertical synchronization in game settings not only don't improve the game quality, but also reduce the performance and load, which leads to similar problems.
Option 3: You can download a performance and temperature checker from NVIDIA's website, which will monitor the performance and temperature of your graphics card in real-time, to see if there is a possibility that the temperature is too high, resulting in a lack of power and ultimately 100% CPU usage.
Option 4: In the NVIDIA control panel, besides setting the “Preferred Graphics Processor” of the global environment to the dedicated GPU, you can also change the games you play, because sometimes the global environment changes may not work in some games or some environments.
I sincerely hope that the above solution will solve your problem. Please feel free to contact me if you encounter any problems!
We look forward to hearing back from you.
Best Regards
Arthur Sheng | Microsoft Community Support Specialist