I didn't do anything for legacy USB Stuff, only legacy RST (Hard drives). You need to test with MBR partitioned hard drive, that is only thing I made changes in regards to.
And secure boot needs to be disabled, and "Other OS" selected if you can instead of "Win8/Win10"

@Lost_N_BIOS :
i understand , but how can i install the windows legacy mode if usb legacy not work?
i will try to install windows in other laptop and after put the hard disk on gx501gi to see if boot.
Thank you.

I see where you're going now, sorry! You would have to use CD/DVD ISO, or put in a MBR disk with windows already installed.
Or I can enable legacy USB in the BIOS, if you would have mentioned that before I would have done already, sorry we didn't consider this until now!

I checked your BIOS, and BIOS images, you have legacy USB support in BIOS settings on advanced page, did you set that to enabled (It should be by default)? I also checked hidden USB Settings and XHCI USB legacy support is enabled by default too.
Are you sure your USB device formatted to MBR? Did you check "Add new Boot option" and see if you can choose/add USB without the UEFI at beginning of name?

legacy usb is enabled but dosent boot... i dont know why...
i tryed with dvd windows installer but goes on uefi ...... i will try this weekend to put another hard drive with windows already installed on MBR partition to see if boot.

in this bios its not possible to add CSM Support? i think this is the problem here.
Thank you

@Fernando :

i told you Samsung 960 pro NVMe SSD work well on legacy mode and boot well on my asus rog strix laptop. i will show you more imgs

check my last image you will see samsung 960 pro have only 2 partition, if you install windows on uefi mode you wil see at least 3 partition.

And no recovery partition. when install windows on uefi mode automatly windows create recovery partition. on last image you can see no recovery partition.

@Fernando :

the Asus gx501gi comes with Samsung MZVKW5

Hi. i have a laptop Pegatron A35FE (old bios 209 - w25q32 Windows 7), and found official firmware for A35FE ( Win8), and she size to 8 mb. The official version of
several files: A35W8PG.506.PH ~8.4 mb, A35W8PG.506.CAP ~ 3.2 mb. How to prepare the firmware for the TL866 programmer, and is it possible? Is it possible to transfer dmi data
from an old dump (w25q32bv 4 mb) to a new dump (w25q64bv 8mb). Flash I already ordered (w25q64bv) in a Chinese store.
i prepared an old dump of the programmer, and a new one

@alex0506 - what is the LAN MAC ID on this system?

Hi!
lan: 4C:72:B9:63:9C:9A

Thank you, found three instances all in same module, two of which may be part of UUID/Serial etc. Standard DMI data is unpopulated per Asus usual (SN12345678901234567), but I know they often use UUID or DTS key that's part LAN MAC and SN
Can you check with AIDA64 (Computer, Summary at bottom - DMI info) and see if you find valid info for UUID and SN, if yes post or PM it to me, thanks. Also, please check front and back of board, as well as side of 24 pin, and top/bottom of PCI/PCIE slots for stickers and send me images of all that in a zip
Thanks!

Hi, i found the stickers behind the laptop and under the battery, and another one with pсi ddr3

Thanks for the images, some might help. Seeing the yellow sticker on ram reminded me, sometimes there is a sticker under the ram slots too (Remove ram), can you check that easily, if yes please check.
Also, if system still running, please run this command and send me image of output (For UUID) >> wmic csproduct get uuid