Been struggling with XP themes and how .net treats those controls. Realised that there is a Application.EnableVisualStyle( ) method that lets you use the XP style rendering of controls. But the FlatStyle property needs to be changed to System for those controls deriving from ButtonBase, GroupBox, or Label (for others its a default). After doing all this the application looked quite OK with the buttons looking like XP buttons, the tabbed windows changing colors to the XP theme, and the group box corners getting rounded.

If the System style is used, the appearance of the control is determined by the user's operating system and the following property values will be ignored: Control.BackgroundImage, ImageAlign, Image, ImageIndex, ImageList, and TextAlign. In addition, the Control.BackColor property will be ignored for button controls. If supported, users can change the appearance of controls by adjusting the appearance settings of their operating system.

CAUTION   Setting the FlatStyle property to FlatStyle.System is not advisable if you need to display an image on a control, display an image as a control's background, or perform precise text alignment.

However my application puts a group box inside a tab page. Therein lies the problem.

http://www.codeproject.com/csharp/dotnetvisualstyles.asp

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemwindowsformsflatstyleclasstopic.asp

http://msdn.microsoft.com/library/?url=/library/en-us/dnwinforms/html/xpthemeaddin_.asp?frame=true

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnwxp/html/xptheming.asp

http://www.codeproject.com/cs/miscctrl/themedtabpage.asp

http://www.binarymission.co.uk/binarysmartbutton.aspx

http://www.dotnet247.com/247reference/msgs/10/53683.aspx

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconrenderingwindowsformscontrol.asp

http://www.codeproject.com/managedcpp/ManagedUxTheme.asp

http://www.infragistics.com/products/lookandfeel.asp?sec=5&cat=-1

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnvssamp/html/vbcs_xpthemesupport.asp