In you skin's ipb_styles.css, find:
 
table.ipb_table .subforums { margin: 2px 0 3px 5px; padding-left: 20px; background: url({style_images_url}/subforum_stem.png ) no-repeat left 4px;} table.ipb_table .subforums li.unread { font-weight: bold; }
 
 
replace with:
 
table.ipb_table .subforums { margin: 2px 0 3px 0px; padding-left: 0px; overflow: hidden;}table.ipb_table .subforums li{ background: url({style_images_url}/subforum_nonew.png) no-repeat left 3px; width: 38%; padding: 4px 17px 4px; margin: 0; float: left;}table.ipb_table .subforums li.unread { font-weight: bold; background-image: url({style_images_url}/subforum_new.png); }
 
Save.