How to change boot priority in ubuntu

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http://askubuntu.com – So i have a laptop with ubuntu installed as the only OS. I also have a USB stick with a windows 7 installation on it. I want to install windows form the USB stick on my laptop but when ii try to restart the laptop to get acces to Bios i cant seem to find the command for it, its like it skips everything and just says ubuntu and then takes me to the login screen. So im wonder how to change the boot priority to USB in ubuntu. (HowTos)