I usually install OEM drivers manually. I really recommend going to the laptop's website(Asus?) and finding your specific model's support page. Then compare the driver versions they have for what you have. Be careful to get the right match for your current OS(8.1 64bit). I'd pay attention to the chipset drivers especially as well as BIOS. The chipset drivers can have a hand in how the OS see's the rest of the hardware.
Be, very careful if you flash BIOS. It can be simple and painless or potentially bricking your laptop permanently(at least till its in a shop that might be able to correct). If you have to flash the BIOS and do so successfully you may need re-configure them to use the dedicated dgpu(gtx 850m) over the integrated.
Is 8.1/64bit the laptop's native OS? If not, its possible there might not be complete current OEM drivers for that.