Two Qs about getting windows info by c# code

[C# Programming]

http://www.barakasoft.com/script/Forums/Images/smiley_mad.gif http://www.barakasoft.com/script/Forums/Images/smiley_snore.gif I wanna know how can I get all the windows_user_names not only the current user_name + getting the domain name of the computer in a LAN network . I need these urgently , please!