unable to boot ubuntu 12

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http://askubuntu.com – i'm trying to dual boot my new laptop, downloaded the latest version of ubuntu 64 bit, burnt it to a dvd, it boots as it's supposed to on my brother's laptop, not on mine, i did everything i could, modified the boot configuration using easybcd, still doesn't boot into ubuntu, from the boot menu i only see windows 7, when i installed linux mint 2 days ago it booted correctly, had to remove it coz i faced installation errors and switched to ubuntu to try it, it just doesn't boot no matter what. how can i fix this? i don't see no errors and i have pressed all the f buttons, i just see windows (HowTos)