I'm assuming that you probably want to create more controls than a button.
You would need to use the "UserControl" class. Override theOnPaint, then in theon-paint method, you would paint a circle that looks like you want. Then on MouseDown you would paint it different to make it looked like it is pressed (for your button example).
To make it even better, I would make the Region of the control a circle, that way the click events would only work in the actual circle.
You can make a user control look however you want or contain any controls you want. For example, you could makea sincle control that contains a label, textbox and a button. If you are wanting to create your own controls, the UserControl class is the way to go.
Ken