Windows XP and Windows 11 on one computer

I have a Asus Expert Centre D700SC computer with Windows 11 installed when bought. What I am trying to do is fit another hdd ( done ) and install windows XP onto it.
I am unable to set the boot to the usb drive that has got windows XP on it. I have managed to set the boot on other computers before, but am unable to do so on this one.