Can't install Windows 10 from USB flash (Legacy BIOS 3602, 2 MBR drives, Asus p8z68 deluxe)

Dec 20, 2018
So i've tried to install windows 10 via a usb drive (downloaded iso from microsoft mediacreationtool). When i installed it as a UEFI compatible, it just loaded then gave me a win 10 BSOD telling that the digital signature couldn't be verified, or sth like that, as if it was not loading the installer but trying to load the USB as a system itself. When i installed it as legacy compatible (which should be my one) and set it up as boot priority, it just told me to press a key to boot from USB, then it didn't do anything (a flashing _ on the top left of the screen), and nothing happens.
If i dont press any key, it just starts windows as usual.
I don't have a secure boot check in my BIOS, nor a legacy start. It's an ASUS p8z68 Deluxe motherboard with bios 3603 on it.
The windows installed file itself isn't and can't be corrupted, as i formatted the USB driver several times, used several methods for formatting it (command prompt etc..) and redownloaded the installer itself but still it didn't give me anything. All of my HDDs are MBRs.