WPF Single Instance

http://pietschsoft.com/post/2009/01/Single-Instance-WPF-Application-in-NET-3.aspx
http://social.msdn.microsoft.com/forums/en/wpf/thread/e321cc4b-e2f3-474e-9575-bacbd2e83a60/
http://msdn.microsoft.com/en-us/library/ms771662.aspx