WAMPSERVER apache2.2 - mod-auth-sspi: how to setup it so I can retrieve windows username

Question

I'm using WAMPSERVER apache2.2.

I've installed mod-auth-sspi, and setup it this way:

<Directory ...>
    AuthName "DOMAIN"
    AuthType SSPI
    SSPIAuth On
    SSPIAuthoritative On
    SSPIDomain "DOMAIN"
    SSPIOmitDomain On
    SSPIUsernameCase "upper"
    SSPIPerRequestAuth On

    Require valid-user
</Directory>

But my problem is that _SERVER["REMOTE_USER"] is filled with the username of the windows account running the server and not with the visitor's.