public static void RunWithPrivilege( string privilege, bool enabled, PrivilegedCallback callback, object state)
        {
            if ( callback == null )
            {
                throw new ArgumentNullException( "callback" );
            }

            Privilege p = new Privilege( privilege );

            try
            {
                if (enabled)
                {
                    p.Enable();
                }
                else
                {
                    p.Disable();
                }

                callback(state);
            }
            catch
            {
                p.Revert();
                throw;
            }
            finally
            {
                p.Revert();
            }
        }