New user: issues while installing Ubuntu 12.04

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http://askubuntu.com – I set up Ubuntu 12.04 desktop on a pendrive. I boot it by pressing F12 when the computer is turned on. I choose any of the options, for example, install on a hard drive (which is what i'm looking forward to do). Ubuntu seems to load, and the desktop background and the mouse pointer appear, but it won't load any further. What's the problem. Help, please, the same happened with Linux Mint 12... what can i do? (HowTos)