When using Windows Vista with a touch-enabled display, the default “press and hold” behavior is to perform the equivalent of a mouse right-click. This may be configured through the Pen and Touch control panel.
Ordinarily, when you press a finger to the touch screen and hold, an animated ring starts to appear to indicate that you are entering the “press and hold” mode. If you wait for the ring to complete drawing and then remove your finger, the ring should disappear and the context menu should be displayed.
In rare instances, if you quickly move your finger while removing it from the screen, the context menu will not be displayed, and instead the “press and hold” ring will stay on the screen and finger touch may no longer function correctly.