i just bought a  XPS 8700 with an added discrete video card ( NVIDIA GeForce GTX 745). i also have two U2415 Monitors, and i use one monitor connect to the lower HDMI port by using the HDMI cable, another one connect to the integrated HDMI port. but it doesn't work, i was try to the following thing, but it still not working, 

• Power on the system
• Press F2 when you see Dell logo onscreen
• Highlight Advanced -> Onboard Device Configuration and press Enter
• Check if you have Intel Multi Display option and Enable it if it is disabled

so please tell me how to connect XPS with two U2415 monitors??