You need to download and extract teh Intel RST drivers for your system.
It's available here.
https://support.hp.com/th-en/drivers/hp-elitedesk-800-g2-small-form-factor-pc/7633277
Download the executable and open it using 7-Zip. Extract the contents to your USB setup disk.
On this screen, click Browse and point to the Intel RST driver folder on the USB setup disk..