Not booting from usb

[abcd_57]

Hello,
i have tried to change the first boot device priority to usb-zip , but it is not booting from it. i am using XP OS and booting ubuntu 12

 

[xtcx]

Did you make sure, the boot files are burnt properly into USB drive?.
This should not be a problem though. I've tried it several times...

 

[abcd_57]

thanks for reply..
yes i have burned the iso file in usb using this software "UNetbootin"

while selecting first boot device which option i have to select
usb-zip
usb-hdd
usb-cdrom
usb-fdd
??