Still using the Tweny Ten Theme by WordPress.org? I'm not surprised at all considering the number of daily downloads to this date of this wonderfully simple Theme
WordPress Theme Installation:
Log in to WordPress and go to Appearance menu, Themes sub-menu, click in Install Themes tab and select Upload option. Upload the zip file and activate the theme. You can as well upload the theme using a FTP client to your wp-content/themes folder and activate it from your WordPress dashboard.
Change of background image or color, header image or custom menu can be done under the Appearance menu from your WordPress dashboard.
License: GNU General Public License, version 3 (GPL)