I just bought a brand new Aspire V5-573G with an i5-4210 (HD4400) and a GTX 850M.
On Windows 7 64bit, I installed all drivers there are (Intel USB 3.0, Intel Chipset, Intel WLAN+Bluetooth, Intel GFX, Realtek Audio, Realtek LAN and Realtek Cardreader, and whatever i forgot to mention).
Overall, there are no other devices recognized with missing drivers except "3D Video Controller" in the device manager. When trying to install the mobile drivers (either 337.88 WHQL or 340.43), the installer aborts on "Checking system compatibility" with "This graphics driver could not find compatible graphics hardware.".
AIDA64 sees the 850M card just fine. Theres no BIOS option for optimus on/off or anything. I don't get it why it wont work.
I am already on the latest BIOS version (2.28) which should enable said feature... Can anyone help me out?