Kir,
If combining the on board Intel® HD Graphics with a external PCI/PCIe video card, Windows will allow using the two graphics controllers at the same time, but the only dual display mode available is "Extended desktop". If you are looking for other dual display options like "Clone display" then it will be necessary to connect the two monitors into one of the graphics solutions, the on board or the video card so Windows will give you the dual display modes available depending on the graphics adapter.
In order to accomplish this, the most important thing is to change some settings on the BIOS. Please go to the configuration tab>video>integrated graphics device> set to “always enable”
Regards.