If a metric definition is read-only, all metrics associated with it are read-only, however it's possible for some child objects to be read-only even if a definition is not. When read only, no new metrics can be added however display values can be changed.
Requirements
Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2