public static DateTime GetLastWriteTime(int hive, String subkey)
            {
                UIntPtr hKey = UIntPtr.Zero;
                int result = RegOpenKeyEx(hive, subkey, 0, KEYREAD, ref hKey);
                if (result != 0) {
                throw new System.ComponentModel.Win32Exception(result);
                }

                StringBuilder lpClass = new StringBuilder(1024);
                IntPtr lpcbClass = IntPtr.Zero;
                IntPtr lpReserved = IntPtr.Zero;
                uint lpcSubKeys;
                uint lpcbMaxSubKeyLen;
                uint lpcbMaxClassLen;
                uint lpcValues;
                uint lpcbMaxValueNameLen;
                uint lpcbMaxValueLen;
                uint lpcbSecurityDescriptor;
                FILETIME lastWriteTime = new FILETIME();
                result = RegQueryInfoKey(hKey, out lpClass, ref lpcbClass, lpReserved, out lpcSubKeys, out lpcbMaxSubKeyLen,
                     out lpcbMaxClassLen, out lpcValues, out lpcbMaxValueNameLen, out lpcbMaxValueLen,
                     out lpcbSecurityDescriptor, ref lastWriteTime);
                RegCloseKey(hKey);
                if (result != 0) {
                throw new System.ComponentModel.Win32Exception(result);
                }

                byte[] high = BitConverter.GetBytes(lastWriteTime.HighDateTime);
                byte[] low = BitConverter.GetBytes(lastWriteTime.LowDateTime);
                byte[] buff = new byte[high.Length + low.Length];
                Buffer.BlockCopy(low, 0, buff, 0, low.Length );
                Buffer.BlockCopy(high, 0, buff, low.Length, high.Length );
                long time = BitConverter.ToInt64(buff, 0);
                return DateTime.FromFileTimeUtc(time);
            }

        public static DateTime FiletimeToDateTime(FILETIME fileTime)
        {
            if ((fileTime.dwHighDateTime == Int32.MaxValue) ||
                (fileTime.dwHighDateTime == 0 && fileTime.dwLowDateTime == 0))
            {
                // Not going to fit in the DateTime.  In the WinInet APIs, this is
                // what happens when there is no FILETIME attached to the cache entry.
                // We're going to use DateTime.MinValue as a marker for this case.
                return DateTime.MaxValue;
            }
            //long hFT2 = (((long)fileTime.dwHighDateTime) << 32) + fileTime.dwLowDateTime;
            //return DateTime.FromFileTimeUtc(hFT2);

            SYSTEMTIME syst = new SYSTEMTIME();
            SYSTEMTIME systLocal = new SYSTEMTIME();
            if (0 == FileTimeToSystemTime(ref fileTime, ref syst))
            {
                throw new ApplicationException("Error calling FileTimeToSystemTime: " + Marshal.GetLastWin32Error().ToString());
            }
            if (0 == SystemTimeToTzSpecificLocalTime(IntPtr.Zero, ref syst, out systLocal))
            {
                throw new ApplicationException("Error calling SystemTimeToTzSpecificLocalTime: " + Marshal.GetLastWin32Error().ToString());
            }
            return new DateTime(systLocal.Year, systLocal.Month, systLocal.Day, systLocal.Hour, systLocal.Minute, systLocal.Second);
        }

 public static extern int GetFileTime(HANDLE hFile, ref FILETIME lpCreationTime, ref FILETIME lpLastAccessTime, ref FILETIME lpLastWriteTime);

 public static extern Boolean FileTimeToSystemTime(ref FILETIME lpFileTime, 
     out SYSTEMTIME lpSystemTime);

 private static extern unsafe bool CertGetCertificateChain(IntPtr hChainEngine, SafeCertContextHandle pCertContext, FILETIME* pTime, SafeCertStoreHandle hStore, [In] ref CERT_CHAIN_PARA pChainPara, CertChainFlags dwFlags, IntPtr pvReserved, out SafeX509ChainHandle ppChainContext);

 public static extern int GetThreadTimes(IntPtr hThread, ref FILETIME lpCreationTime, ref FILETIME lpExitTime,
                                         ref FILETIME lpKernelTime, ref FILETIME lpUserTime);

 public static extern int SetFileTime(IntPtr hFile, ref FILETIME lpCreationTime, ref FILETIME lpLastAccessTime,
                                      ref FILETIME lpLastWriteTime);

 public static extern int CompareFileTime(ref FILETIME lpFileTime1, ref FILETIME lpFileTime2);

 public static extern int FileTimeToDosDateTime(ref FILETIME lpFileTime, ref int lpFatDate, ref int lpFatTime);

		[DllImport("kernel32", CharSet = CharSet.Unicode)] public static extern int SetFileTime(HANDLE hFile, ref FILETIME lpCreationTime, ref FILETIME lpLastAccessTime, ref FILETIME lpLastWriteTime);

		[DllImport("kernel32", CharSet = CharSet.Unicode)] public static extern int SystemTimeToFileTime(ref SYSTEMTIME lpSystemTime, ref FILETIME lpFileTime);

		[DllImport("kernel32", CharSet = CharSet.Unicode)] public static extern int FileTimeToDosDateTime(ref FILETIME lpFileTime, ref int lpFatDate, ref int lpFatTime);

		[DllImport("kernel32", CharSet = CharSet.Unicode)] public static extern int FileTimeToLocalFileTime(ref FILETIME lpFileTime, ref FILETIME lpLocalFileTime);

 internal static FILETIME DateTime2FileTime(DateTime dateTime)
 {
     long fileTime = 0;
     if (dateTime != DateTime.MinValue)      //Checking for MinValue
         fileTime = dateTime.ToFileTime();
     FILETIME resultingFileTime = new FILETIME();
     resultingFileTime.dwLowDateTime = (uint)(fileTime & 0xFFFFFFFF);
     resultingFileTime.dwHighDateTime = (uint)(fileTime >> 32);
     return resultingFileTime;
 }

        internal static DateTime FileTime2DateTime(FILETIME fileTime)
        {
            if (fileTime.dwHighDateTime == 0 && fileTime.dwLowDateTime == 0)    //Checking for MinValue
                return DateTime.MinValue;

            long dateTime = (((long)fileTime.dwHighDateTime) << 32) + fileTime.dwLowDateTime;
            return DateTime.FromFileTime(dateTime);
        }

 public static extern Boolean GetFileTime(IntPtr hFile, FILETIME lpCreationTime,
     out FILETIME lpLastAccessTime, out FILETIME lpLastWriteTime);

 public static extern int RegEnumKeyEx(IntPtr hKey, int dwIndex, string lpName, ref int lpcbName,
                                       ref int lpReserved, string lpClass, ref int lpcbClass,
                                       ref FILETIME lpftLastWriteTime);

 public static extern long FileTimeToSystemTime(ref FILETIME FileTime, 
     ref SYSTEMTIME SystemTime);

 public static extern int RegQueryInfoKey(IntPtr hKey, string lpClass, ref int lpcbClass, ref int lpReserved,
                                          ref int lpcSubKeys, ref int lpcbMaxSubKeyLen, ref int lpcbMaxClassLen,
                                          ref int lpcValues, ref int lpcbMaxValueNameLen, ref int lpcbMaxValueLen,
                                          ref int lpcbSecurityDescriptor, ref FILETIME lpftLastWriteTime);

        public static string ToStringFromFileTime(FILETIME ft)
        {
            DateTime dt = FiletimeToDateTime(ft);
            if (dt == DateTime.MinValue)
            {
                return string.Empty;
            }

            return dt.ToString();
        }