Hi!
I've not tried XP on NUCs but from my experience you'll have to set the legacy boot in the BIOS first, as WinXP might not start on UEFI. Besides that, there is no official driver for WinXP in Haswell NUCs Download Center -- WinXP could potentially start on the default drivers. As a workaround, you may try using WinXP drivers for Ivy Bridge NUCs Download Center
Hope that helps