[SOLVED]Can't boot into ubuntu 12.04, grub menu wont show

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http://askubuntu.com – I downloaded the Ubuntu 12.04 64bit and installed it on a 115GB partition next to a 15GB swap alongside Windows 7. I'm using a asus g73s. I have 2 drives: one with only Windows (500GB) and another with a partition for (250GB) Windows and (115GBb) the Ubuntu and (15GB) swap partitions. But after the installation, I can't find out how to run Ubuntu. It just run windows. I read that it should show a grub menu. I tried: Holding both Shift keys at boot up. Running the Ubuntu Live CD and edit the grub file. Also pressing the Esc and some function button during boot. Nothing seems to work. (HowTos)