[System] installed kubuntu 13.04 but it did not shows up

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http://www.kubuntuforums.net – hi i have installed successfully kubuntu-13.04-desktop-amd64 and at the end i pressed restart now as it says then black screen asked me to remove the disc then press enter but at this point the system freezes and nothing happened. so i had to press the restart button but the system goes directly to windows 7 and did not recognize kubuntu what should i do ?? ------ i have windows 7 x64 on c drive 16gb ram 1TB hdd ( 400gb c drive + 80gb kubuntu ) MB: GA-Z77X-D3H gigabyte ------- P.S. i did installed kubuntu and ubuntu on my old pc desktop with xp pro few years ago (HowTos)