list username of the computer

You can use WMI to get all records of the type Win32_UserAccount. Please see:
http://en.wikipedia.org/wiki/Windows_Management_Instrumentation[^],
http://msdn.microsoft.com/en-us/library/windows/desktop/aa394507%28v=vs.85%29.aspx[^].

This is how to write it in C#: http://stackoverflow.com/questions/5247798/get-list-of-local-computer-usernames-in-windows[^].

For a currently logged user, use: System.Environment.UserName: http://msdn.microsoft.com/en-us/library/system.environment.username.aspx[^].

Problem solved.

—SA