Whilst it would be ideal for you to find out what is causing the problem and resolve it, in your case as a Linux tyro I would go for a complete format and fresh installation. Rather than Ubuntu, I would recommend you download whichever version of Linux Mint you prefer (the versions revolve around which desktop you want, Gnome or KDE).
Mint is a refined product originally developed from Ubuntu, but which now also includes direct access to the Debian packages too. It also provides the appropriate media codecs to allow you to view dvds and other media files which Ubuntu does not.