Not Able to boot after installing ubantu 12.10 and 12.04

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http://askubuntu.com – I am using intel based acer laptop and first time I installed kubantu 12.10 but I got blank screen. After this I tried Ubuntu 12.04 but the result is same. Please help me. I tried many times but the result is frustrating. If I am connect to external screen I am able to see my screen on extenal device. I have also tried with F6 and selecting kernal but it does not work. I have tried several options but I am not able to boot my system. I do not have any operating system , earlier I was using windows 7 but now I am trying to install only linux based operating system. (HowTos)