zer0nes

I recently purchased a vaio SVE15129CN laptop and have been trying to install ubuntu with a bootable pendrive. However despite the fact that I have set the priority of external drive boot above internal hard disk and have also enabled booting from external drive, every time I start my laptop it loads windows 8 from my internal hard disk. I have tried booting from the same pen drive in my old DELL Inspiron and it works fine. Can anyone suggest a solution.