The options to use the integrated processor graphics and a discrete controller at the same time, depends on the implementation and software that has been used by the motherboard or Original Equipment Manufacturer to achieve this.
In this particular case we suggets you to formward this type of concerns directly to your computer manufacturer for further research.
This thread confirms my info http://communities.intel.com/thread/24946?tstart=0, With Latest driver Dual digitally connected monitors not working, even without discret video! Any suggestions? And another bug with dual cards - when install driver for discrete radeon card with enabled integrated GPU, screen gooes black and don't come back. Only reboot helps, so the only possible way to install driver - disable integrated gpu in BIOS. This is yours driver problems, not others, so don't kick me out like a ball.