This simple and brief tutorial is going to show you how to quickly restore the Unity default icons, window decoration, cursor, and GTK theme in Ubuntu 13.04 Raring Ringtail.
First go to Ubuntu Software Center, search for and install “unity tweak tool”:
Unity Tweak Tool is a simple configuration software for Unity Desktop Environment. Once installed it, launch and go to Appearance -> Theme. You’ll see the window as below:
At the bottom of each tab, there’s a “Restore Defaults” button, click on theme and you’ll get the original themes.