Petzold's book has information on radial panels (pie menus) which is a good starting point. Also, pie menus are sometimes referred to as circular context menus. You'll probably have to use Windows Presentation Foundation to develop your pie menu.
FYI. a pie menu is a circular graphical menu similiar to slices of a pie. Each slice is a different menu option. Thus, clicking on one slice might open a file while clicking on another slice might print the file etc.