Install a proper "monitor driver" for your new display. It's usually not automatic. Let's find a link about this process.
In this case the video card is fine with the old display so I want to read how you get this monitor supported.
I wanted to change the monitors around on two of the desktops that I owned. The Hp a6720y came as a bundle with a HP 23" LCD monitor. I wanted to take the 23" and swap it with my 15" Polaroid HDTV Monitor so that my gaming computer could more competently utilize the larger screen.
When plugging up the 15" to the HP a6720y, VGA cable, the Polaroid HDTV monitor works, with one major problem... the monitor repeatedly "flashes." Their is set time for when it flashes, it simply goes black then back to normal, displaying the resolution and "D-Sub" in the upper right hand corner. It does this over and over with no real rhythm or instigation.
I have no clue why it's doing this, or how to fix it. It could be the onboard Nvidia geforce 9100 integrated chipset, but I don't know for sure. If anyone could help me this would be greatly appreciative, I can supply any information you need, just let me know. Thanks so much for your time.