if you disable the video card in bios the computer will revert to either whatever video your motherboard supports or any integral video that is build into your system if you have an after market card that is running.
In the case of a Lenovo Z565 laptop with the HD 5470 option the motherboard HD 4270 is inactive by default when there is a working discrete video card in the system.
There is no BIOS option for deactivating video adapters.
In the old school systems you need to configure a jumper on the motherboard to choose between different hardware configurations.
Later improvements let you make some of those same configurations options in BIOS menus.
Most recent systems - and that includes the Asus N53Jg - will handle that automatically without the need of setting jumpers or making changes in the BIOS settings.
In the case of your Asus N53Jg it has the NVIDIA Optimus feature. BOTH GPUs will be in an active state and the active GPU will be chosen by the system based on the video workload demand.
For all basic 2D office/school work the Nvidia GT 415M discrete video card will be powered down and the system will use the Intel HD GMA which is the onboard GPU included in the CPU package of the Core i3/i5/i7 mobile CPUs.
When the system has an increased video workload (gaming or HD video encoding, etc) it will power up the GT 415M and use that.