I have a 3470 HD card in a Windows 10 Home 64-Bit HP Desktop.
When I use the older 8.970.100.9001 driver, the OS detects the dual HP EliteDisplay E201 monitors with no problem and I can extend across.
If I upgrade to the latest 15.7.1 driver, the display works fine, but the OS can't see that I have two monitors attached. All it does it duplicate the screen on both. I'm unable to extend.
Normally, I wouldn't complain about using the older driver, but every so often the driver crashes, I have to boot into safe mode, change to the newer driver, then rollback to the older one.
It's become a giant pain.