[ubuntu] windows 7 boots automatically, no option to boot ubuntu

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http://ubuntuforums.org – I have just got a new Dell inspiron laptop which comes with windows 7. I wanted to setup up a windows 7/ubuntu 12.04 dual boot system. I used a USB stick which has a copy of ubuntu 12.04 64 and booted from the USB stick. It took me through the installation process (which involved partitioning the hard disk o make room along side of windows). Installation completed and then it restarted the computer. After restarting, the computer booted straight into windows with no menu with the option of ubuntu or windows like I expected. Can anyone help me boot into ubuntu? (Hardware)