Not booting properly.

Hello,
I have done that which you sugested for me to do but still, my notebook system prompt me to select the O S. Which i choose Ms windows xp professional rather than USB repair Not to start Ms windows XP PRO.After a few seconds, a blue screen came out again with thesame prompt. " unamountable_boot_volume" that's the only thing I could see before the screen went off and the system went back as if it was just powered on.
thank you for your technical support.