I've downloaded the USB version from the web site, and the USB Installer, then I run it and it finished, but then nothing happens, I tried to go to ISO and run the setup then It finished and restarted the computer with Windows, Iv'e tried to restart it again and choose Ubuntu but it launches a black screen with some texts and nothing happens, please help me I'm very new to Ubuntu and I need to download it because my Windows is pretty awful!