M4800 Unable to duplicate the screen

Hi Dellers

I have a M4800 with due graphics card, one intel HD 4600, one AMD FirePro M5100.

After I upgraded to Win8.1, some how I can not duplicate my screen anymore. No matter what I connected, TV, Monitor, Projector, they are all the same.

I can Extend my screen or use second screen only or Built in Display only mode. They all detected 2 screens one is built-in plus another device. However, when I switch to duplicate mode, it shows 3 devices, built-in, second plus the THIRD ONE, and I can only duplicate 1 and 3, but I can't duplicate 1 and 2.

Anyone can help me with this problem? I find a lot of ppl have the same problem as me, and I tried to re-install the drivers for both graphic card but nothing changed.

Many Thanks!