can't boot from usb (working on other comp.)

[m-blue]

Hello,
I am new user of x61s, now I have windows 7, but I would like to put my old hdd and reinstall xp - faster for while....
I am trying to use my pendrive with usb win xp instalation - nothing, I have hirens boot cd on the other usb - the same - no response from usb.. I can choose usb as drive to boot, but after this screen is black ( normal dos) and cousor is blinking at up left corner...
Anybody can help?
I have latest bios, I was trying to left only usb as drive to boot in bios - usb was first to boot - everything;/
Michal