http://msdn.microsoft.com/library/default.asp?url=/library/en-us/wmisdk/wmi/win32_displayconfiguration.asp

Looks like all the properties for that class are read-only. Another thing.. I'm 99% sure the WQL interface as microsoft affectionately calls their ODBC'ish interface to WMI can only be used to query information - you can't set things through it.(even if they're not read only) So if you're wanting to modify values or execute methods you must use the WMI object interface.

Update: Here's a paste from MSDN A developer making a query to WMI must use the WMI Query Language (WQL). WQL is a subset of the ANSI standard Structured Query Language (SQL), with WMI-specific extensions. Because WQL is a read-only query language, a developer cannot use WQL to instruct the Windows Management service to update, insert, or delete data in the WMI repository or in a provider. Instead, a developer can only use WQL to retrieve information. For more information, see Querying WMI.