USB cannot boot for win 7 iso instalation

This is what is shown on the computer when I want to get into the xp of another computer that I own.

I want to boot from USB but it wont allow it!
I went to BIOS and checked the sequence and it goes 1 USB, 2 DiSK, 3 CD...

What else can I configure so it will start up the ISO on the USB?

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