Once your install is loaded press F10 that will bring up a Elevated CMD. See this
thread in the G75 Stickys This thread was for the G75 but applies to the G750
It's best to set up a USB thumb Drive as the install media this thumb drive needs to be formatted Fat 32. Rufus seems to be the best program to put the install media together successfully for UEFI GPT systems
C:\> Diskpart
DISKPART> list disk
DISKPART> select disk (id)
DISKPART> clean
DISKPART> convert gpt
Continue with the install you should be installing to a Disk/SSD not to a partition as UEFI needs to set up partitions its best to start from a CLEAN Disk/SSD. And remove your 2nd hard drive before you start
G752VY-DH72 Win 10 Pro
512 GB M.2 Samsung 960 Pro
1 TB Samsung 850 pro 2.5 format
980m GTX 4 GB
32GB DDR 4 Standard RAM
Z97 PRO WiFi I7 4790K
Windows 10 Pro
Z97 -A
Windows 10 Pro