DirectoryServices - “Network logon failure unknown user name or bad password”
//Example 1: Find all users in Active Directory. Be sure your LDAP connection string is correct.
string ldapConnection = @"LDAP://sergio-j9i2vccv/dc=contoso,dc=com";
string username = "Administrador"; //I'm using a spanish version of WS2003.
string password = String.Empty;

UserFinder userSearcher = new UserFinder(ldapConnection, username, password);
try
{
    var users = userSearcher.FindAllUsers();

    foreach (var user in users)
    {
        Console.WriteLine(user.Name);
        Console.WriteLine(user.Path);
    }
}
catch (Exception e)
{
    Console.WriteLine(e.Message);
}