I think this article might help you.
Let me know if you face any problem while understanding the code.
Edit 1 : I am confused with your question.
  my idea: According above Windows shoud
  be provide some vay to validate and
  enter username and password
Do you want to validate a entered username and password?
Ahh, sorry for the delay. Here's the converted c# code
Add following namespaces:
using System.Security.Principal;
using System.Security.Permissions;
using System.Runtime.InteropServices;
And then here goes the main code :
namespace WindowsAccount
{
    public partial class Form1 : Form
    {
        [DllImport("advapi32.dll", SetLastError = true)]
        public static extern bool LogonUser(string lpszUsername,
            string lpszDomain,
            string lpszPassword,
            int dwLogonType,
            int dwLogonProvider,
            out IntPtr phToken
            );
        [DllImport("kernel32.dll")]
        public static extern int FormatMessage(int dwFlags, ref IntPtr lpSource, int dwMessageId, int dwLanguageId, ref String lpBuffer, int nSize, ref IntPtr Arguments);
        [DllImport("kernel32.dll", SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        static extern bool CloseHandle(IntPtr hObject);
        public static string GetErrorMessage(int errorCode)
        {
            int FORMAT_MESSAGE_ALLOCATE_BUFFER = 0x100;
            int FORMAT_MESSAGE_IGNORE_INSERTS = 0x200;
            int FORMAT_MESSAGE_FROM_SYSTEM = 0x1000;
            int msgSize = 255;
            string lpMsgBuf = null;
            int dwFlags = FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS;
            IntPtr lpSource = IntPtr.Zero;
            IntPtr lpArguments = IntPtr.Zero;
            int returnVal = FormatMessage(dwFlags, ref lpSource, errorCode, 0, ref lpMsgBuf, msgSize, ref lpArguments);
            if (returnVal == 0)
            {
                throw new Exception("Failed to format message for error code " + errorCode.ToString() + ". ");
            }
            return lpMsgBuf;
        }
        public Form1()
        {
            InitializeComponent();
        }
        private void btnLogin_Click(object sender, EventArgs e)
        {
            IntPtr tokenHandle = new IntPtr(0);
            try
            {
                string UserName = null;
                string MachineName = null;
                string Pwd = null;
                //The MachineName property gets the name of your computer.
                MachineName = System.Environment.MachineName;
                UserName = txtUser.Text;
                Pwd = txtPass.Text;
                const int LOGON32_PROVIDER_DEFAULT = 0;
                const int LOGON32_LOGON_INTERACTIVE = 2;
                tokenHandle = IntPtr.Zero;
                //Call the LogonUser function to obtain a handle to an access token.
                bool returnValue = LogonUser(UserName, MachineName, Pwd, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, out tokenHandle);
                if (returnValue == false)
                {
                    //This function returns the error code that the last unmanaged function returned.
                    int ret = Marshal.GetLastWin32Error();
                    string errmsg = GetErrorMessage(ret);
                    MessageBox.Show(errmsg);
                }
                else
                {
                    //Create the WindowsIdentity object for the Windows user account that is
                    //represented by the tokenHandle token.
                    WindowsIdentity newId = new WindowsIdentity(tokenHandle);
                    WindowsPrincipal userperm = new WindowsPrincipal(newId);
                    //Verify whether the Windows user has administrative credentials.
                    if (userperm.IsInRole(WindowsBuiltInRole.Administrator))
                    {
                        MessageBox.Show("Access Granted. User is admin");
                    }
                    else
                    {
                        MessageBox.Show("Access Granted. User is not admin");
                    }
                }
                CloseHandle(tokenHandle);
            }
            catch (Exception ex)
            {
                MessageBox.Show("Exception occurred. " + ex.Message);
            }
        }
    }
}
Let me know if you face any problem.