Did you set BIOS properly?
Win 7 isn't compatible with Secure boot and Fast Boot.
How did you do Win 7 USB drive (Rufus)?
To create a Win 7 USB drive, open a CMD window as administrator and type:
diskpart
list disk (it will list all drives. Identify the USB drive number)
select disk n (replace n by the USB drive number obtained with list disk)
clean
convert mbr
create part primary
select part 1
format fs=fat32 quick
assign
active
exit (to exit diskpart)
If you have a Win 7 installation iso file
On Win 7 use
7Zip to extract all files and folders from the Win 7 iso file to the USB drive.
On Win 10, mount the iso file and copy all files and folders to the USB drive.
To make it UEFI boot able you must add the
\efi\boot folder
To make it universal (all Win 7 versions), go to \sources on the USB drive and delete \sources\ei.cfg
Did you boot the Win 7 USB as Legacy or UEFI?
On BIOS:
Set Disk mode to AHCI, not RAID
Select OS mode = CSM + UEFI or Select OS mode = other + UEFI (depends on BIOS).
Disable fast boot and secure boot
Windows can be installed in two ways: Legacy-MBR or UEFI-GPT
To install as Legacy-MBR you
must boot the installation drive as Legacy
To install as UEFI-GPT you
must boot the installation drive as UEFI.
If you have a UEFI BIOS, you should install as UEFI-GPT
Detach any other drives (SATA or Power cable) from the MB.
During POST, press F12(?) to launch the boot menu. You will see two options for the USB drive. USB UEFI (Name) and USB (Name). Select USB UEFI (Name).
Go to install and delete ALL partitions on the main drive till you have one and only one unallocated space and then proceed.