windows 10 "we couldn't create a new partition or locate an existing..

William40 said:

I have latest bios and I tried everything until I booted as UEFI and set the bios to boot as UEFI so windows installed and converted my drive to GPT. I think 1909 can be only installed on GPT drives , it was a headech

If you look at my system spec, I also have an MSI MB set to both UEFI+Legacy. I have no problem at all installing either GPT or MBR.
I am curious how did you boot your Windows installation media ? Did you use F11 to display BOOT MENU and select correct boot mode as shown in post #3. Note that if you have the BIOS set to UEFI+Legacy, and if you try to boot for Legacy mode and unable then it will boot using UEFI mode.

Another thing to look at is Your Installation Media only boot with UEFI mode. For installation media to boot into Legacy mode, it must be formatted with FAT32 and set to Active ???

I made USB bootable ith Rufus and I choose MBR !!. I entered the bios and choosed to boot from the usb as UEFI then windows setup worked I dont know how.

That might be the problem. Few people in this forum had problem using Rufus to build Installation Media.

FYI, You don't need to use Rufus. Just format the USB with FAT32 and set it Active then mount the ISO, select everything and copy to the USB.

Another option is to extract the ISO to the root folder of the USB using either WinRAR or 7-zip
From Admin command prompt
EX: 7z.exe x -y -oH:\ Win10x64.ISO
where H: is the drive letter of the USB