get the windows user id?

I am writing an intranet program at work and need to access the username of the person that is logged in into windows. Ive been looking and the only things that i find are giving me:

ServerName/ASPNET not the users actual login name.

ive been trying stuff like

system.environment.userName

and

WindowsIdentity.GetCurrent.Name


has anyone ever had this problem? is it something that i have to change in the server settings? or is it a differant function that i need to use.


any help would be appreciated
thanx