Microsoft officially launch this bootable tool easy to make bootable usb i dint test it on xp but i can make windows 7 usb for those machine which don't have Rom or crypt system easy to boot and install windows from usb.
no need of cd rom dvd rom or portable rom just use it and boot from usb devices first in bios it will take half hour to make usb use iso f any windows that you like also install extra plugin which it requires from the link it shows else use it as it is, works on Microsoft devices not on mac or Linux etc ill also try to upload windows xp bootable tool and also try to find some for mac user later on