http://msdn2.microsoft.com/en-us/library/435f1dw2.aspx

The new modifier instructs the compiler to use your implementation instead of the base class implementation. Any code that is not referencing your class but the base class will use the base class implementation.

http://msdn2.microsoft.com/en-us/library/ebca9ah3.aspx

The override modifier may be used on virtual methods and must be used on abstract methods. This indicates for the compiler to use the last defined implementation of a method. Even if the method is called on a reference to the base class it will use the implementation overriding it.

http://social.msdn.microsoft.com/Forums/en-US/65e02299-300f-4b74-8f0a-679f490605f5/new-vs-override-?forum=Vsexpressvcs