Accessing user(groups) defined in NT

[Stilltray]

I want to read the table(s?) where NT4 stores his group- and userdefinitions. With Delphi.
Just readonly.
The reason is to be sure the user or group is known in NT wenn a new (Delphi) application will be installed.
I've Delphi applications, where usernames/passwords are used for authorizing people for (parts of) an application.
Apart from this users have to be defined in NT for logging into the network etc.
Just to be sure both are defined and with the same name etc, it would be nice to use the userinformation as defined in NT in the Delphi applications for authorization.
So I want to build a Delphi application for authorizing the Delphi applications and use the names/groups already defined in NT.
Any idea????