X79 Extreme6 - SSD Windows Install

Hello. After some help. Trying to do a clean install of Windows 10 on a SSD drive on my sons computer (it's a little old, but was running pretty well up until a week ago).

The installation is extremely slow, using USB stick, and after a few hours I get a Install Windows error - Windows could not complete the installation. To install Windows on this computer, restart the installation.

Have read some posts in this forum with similar problems, but unable to follow the instructions, particularly in regard to CSM, I cannot see the option anywhere.

Can access the Asrock UEFI, but configuration options not the same as most of the suggestions in posts.

Specs:
MOBO - Asrock X79 Extreme6 P2.80
CPU - i7-4930K 3.4ghz
RAM - 2 x DDR3_B1 G_Skill 8192MB 667mhz
SSD - Samsung SSD 860 EVO 1TB
GPU - Gigabyte AORUS Radeon RX 580 8GB
Previously had a 256gb SSD with Windows7

All the settings in BIOS have SATA3 as ACHI.

Would appreciate any suggestions on how to fix this problem, get Windows installed and get the rig back in use.

Thanks very much

Hello.
Yes, it does boot up ok - windows 7. Last Thursday began to run extremely slow, with little CPU or RAM usage. SSD was nearly full so decided on new SSD and clean install of Windows 10.
Next thing I was going to try was using an old HDD and see if similar problems.