Is it possible to use the Windows 2003 user names instead of pre-Windows 2000 user names in Windows Authentication?

[MaURiCe]

Hello,
I am trying to get username information by using
User.Identity.Name.ToString, if i logged in with username to given
network place, it is ok! It returns SERVERNAME/username.
Otherwise if I logged in with "name.surname at SERVERNAME.com" it again
returns SERVERNAME/username although i want it to return
"name.surname".
I changed the IIS server settings, checked digest authentication and
tried the other things, too. But makes no difference.
It is said to originated from Kerberos Authentication...
If anyone can help me I will be appreciated.
Thanks for now,
MK