pinging windows 64 bit with ICMP dosn't work ?

using System;
using System.Net;
using System.Runtime.InteropServices;

namespace testPing
{
    class Class1
    {
        public static class ServerStatus
        {

            [StructLayout(LayoutKind.Sequential, Pack = 1)]
            public struct ICMP_ECHO_REPLY
            {
                public uint Address;
                public uint Status;
                public uint RoundTripTime;
                public ushort DataSize;
                public ushort Reserved;
                public IntPtr Data;
                public IP_OPTION_INFORMATION Options;
            }

            [StructLayout(LayoutKind.Sequential, Pack = 1)]
            public struct IP_OPTION_INFORMATION
            {
                public byte TTL;
                public byte TOS;
                public byte Flags;
                public byte OptionsSize;
                public IntPtr OptionsData;
                public int RealOptionData;
            }

            public static class Icmp
            {
                public const int IP_SUCCESS = 0;
                public const int IP_BUF_TOO_SMALL = 11001;
                public const int IP_REQ_TIMED_OUT = 11010;
                [DllImport("icmp.dll")]
                public static extern IntPtr IcmpCreateFile();
                [DllImport("icmp.dll")]
                public static extern uint IcmpSendEcho(IntPtr icmpHandle, uint
                ipAddr, ref int requestData, ushort requestSize, IntPtr optionInfo, ref
ICMP_ECHO_REPLY replyBuffer, uint replySize, int timeout);
                [DllImport("icmp.dll")]
                public static extern bool IcmpCloseHandle(IntPtr icmpHandle);
                public static bool Ping(string host)
                {
                    uint addr =
                    BitConverter.ToUInt32(IPAddress.Parse(host).GetAddressBytes(), 0);
                    IntPtr h = IcmpCreateFile();
                    int req = 123456789;
                    ICMP_ECHO_REPLY rep = new ICMP_ECHO_REPLY();
                    uint retval = IcmpSendEcho(h, addr, ref req, 4, IntPtr.Zero,
                    ref rep, 56, 10);
                    IcmpCloseHandle(h);
                    return (retval != 0 && rep.Status == IP_SUCCESS);
                }
            }
        }

    }
}