This post gives great instructions on installing the G750JS and other models that are not the G750JX:
But the nugget of information is the link to ASUS provided Windows 7 drivers. These laptops are all very similar as you will soon see; but the G750JX has 3 important differences.
1) The BIOS file is very different. Download the latest BIOS file from the G750JX page. As of this writing it's version 209 (it's the same BIOS for Win 8, 8.1, and Other options)
Put the extracted file in an easy to find place (like C:\Bios). Press ESC when the machine is booting to access BIOS (i've seen some peole hold it down, I just click it a lot...). Choose Easy Flash, look for the file through the clunky interface, it will detect the file to be correct and let you flash it.
When you reboot, the BIOS is reset to default settings. You may want/need to disable secure boot and enable CSM to boot to DVD in non-UEFI mode, if that's what you want. I like my things simple so that's how I did mine.
2) You will need the Intel provided ME 8 installer, instead of the one on the ASUS G750JS link. This installer is here:
With those 2 differences out of the way, get the rest from the G750JS Windows 7 x64 driver page at https://www.asus.com/Notebooks_Ultrabooks/ASUS_ROG_G750JS/HelpDesk_Download/
3) This laptop has no Intel integrated card. I used the latest WHQL driver from the Nvidia site (347.25 at time of writing, for a 770M).
My G750JX used the Broadcom wireless card, Broadcom Bluetooth module, and the Atheros NIC. Change those in case your model is different.
This is the order I installed them. I rebooted when any requested since sometimes installers can cause each other problems, and I only wanted to do this once :)
1 intel chipset
2 wireless broadcom
3 intel rapid storage
4 realtek audio
5 lan atheros
6 usb3 intel
7 touch pad elantech
9 keyboard filter (no idea what this does, but OK)
10 bluetooth broadcom (this will require .Net 4 later on)
11 thunderbolt intel ( i dont have any thunderbolt devices, but hey...)
12 card reader genesys (to do this one, I had to first insert a SD card, see the driver half fail, right click the USB Mass Storage in Device Manager, update driver, then uninstall the device and re-insert the SD card - all for USB3.0 on the card reader)
Lastly, the Intel ME you downloaded in Step 2 will take care of the last pending device in Device Manager.
I love this laptop on Windows 7 - next is Fedora 21!