[ubuntu] Problem after installing

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http://ubuntuforums.org – Hi I have just installed Ubuntu 12.04 on my computer but it has a problem when starting. I have installed it before (using the same CD) and it run properly, but now, when starting Ubuntu it doesn´t load and the screen is like moved: It´s divided in the middle and when moving mouse rightward it reapears at the left side, and the "end" of the sides of the screen is in the midle... It does nothing more than what´s in the image. Any ideas? I will try to install it using a pen drive to see if the CD is broken. PD: Sorry about my english, I´m from Argentina and (Hardware)