If i understand from your question correctly, looks like you want to boot from your USB device.
To boot from USB, you need to get into BIOS and set USB the first in the booting priority list. (To do this your BIOS must be supporting USB booting)

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hi
- Visitor 2 years 16 weeks agofirst of all thnks for your help,
i have download super grub disk but i cannot to launch it. i have tried with press f12 at start and with press esc at start but my pc don't see anything and
say
GRUB loading.
error : no such disk
grub rescue>
now my pc go only with cd live of ubuntu 9.10.
if i try to reinstall ubuntu i can see that there still windows xp but don't start, and don't start ubuntu.
how i can know if my bios supporting usb booting? if no can i create super grub in a cd and than start with this?
i need to know thw step to do this...
i hope that my experience with linux don't finish here...
ty for your reason
Carlo