In version 4.0.0, released 25 September 2003, Xfce was upgraded to use the GTK 2 libraries. Changes in 4.2.0, released 16 January 2005, included a compositing manager for Xfwm which added built-in support for transparency and drop shadows, as well as a new default SVG icon set. In January 2007, Xfce 4.4.0 was released. This included the Thunar file manager, a replacement for Xffm. Support for desktop icons was added. Also, various improvements were made to the panel to prevent buggy plugins from crashing the whole panel. In February 2009, Xfce 4.6.0 was released. This version had a new configuration backend, a new settings manager and a new sound mixer, as well as several significant improvements to the session manager and the rest of Xfce's core components.