try this:
1. Open NVIDIA control panel;
2. Manage 3D settings;
3. Global settings tab;
4. Power Management Mode settings, select "Prefer Maximum Performance";
5. See if there's a "Preferred Graphic Processor" setting, change from "Auto select" to "High Performance NVIDIA Processor".
If there's no such option, it means that the integrated gpu is already disabled and it is not the issue there.
If you're using an ATI/AMD card, there's a huge variation between the Catalyst Control Center settings and it may vary, but should be found in advanced mode and be similar to this:
1. Go to "Graphics" > "PowerPlay" - Set Plugged In and Battery to Maximum Performance;
2. If applicable to your graphics card, go to "Graphics" > "3D" and move the slider across to Performance so it is set for Optimal Performance;
Hope this solves the problem.