WCF/WF - how to get logged in user name from window service

how to get logged in user name from window service. when i do the same thing using Environment.UserName i get username as "System".

There are certain number of ways to retrieve the logged in username in windows service which are discussed over here out of which I would prefer by using System.Management
http://www.pcreview.co.uk/forums/thread-3460184.php