How to validate user using Active directory

[kedarrkulkarni]

I m trying to create an application which takes login-Name of user on his computer (which is active directory login). using following syntax

    Dim userAPAC As String
    userAPAC = Request.ServerVariables("LOGON\_USER").Trim()

I dont have admin username and password of Active directory, neither i want to validate user (i dont want to provide password but only username). can i pass only username to DirectoryEntry() class and get information about that user? Thanx !