RadPanelBar has a style named ExplorerBarStyle which resembles the look and feel of Windows XP explorer bar. Actually, RadPanelBar supports four different styles like OutlookNavPane, ExplorerBar, ListBar, VS2005Style. To set a style you should use the GroupStyle property:
.radPanelBar.GroupStyle = PanelBarStyles.ExplorerBarStyle;
I suggest you also take a look at the examples of RadPanelBar in our Demo application. There is a lot of sample code to use.
the Telerik team