Kill unsupported OS test

public sealed class OsVersion
{
    /// <summary>
    /// 太平洋標準時
    /// </summary>
    private static readonly TimeSpan PST = new TimeSpan(-8, 0, 0);
    /// <summary>
    /// Windows NT 5.1(Windows XP)のサポート終了日
    /// </summary>
    private static readonly DateTimeOffset WindowsNT_5_1_End = new DateTimeOffset(2014, 4, 8, 0, 0, 0, PST);
    /// <summary>
    /// Windows NT 5.2(Windows Server 2003, Windows XP x64 Edition)のサポート終了日
    /// </summary>
    private static readonly DateTimeOffset WindowsNT_5_2_End = new DateTimeOffset(2015, 7, 14, 0, 0, 0, PST);

    private delegate void KillOldVersionDelegate();
    private static KillOldVersionDelegate Delegate;
    private static IAsyncResult Result;
    private static Boolean TerminateThread;
    private static readonly String SystemDirectory = Environment.GetFolderPath(Environment.SpecialFolder.System);
    private static readonly FileVersionInfo KernelVersion = FileVersionInfo.GetVersionInfo(SystemDirectory + @"\NTOSKRNL.EXE");
    private static readonly FileVersionInfo HardwareAbstractLayerVersion = FileVersionInfo.GetVersionInfo(SystemDirectory + @"\HAL.DLL");

    public static void KillOldVersion()
    {
        Delegate = new KillOldVersionDelegate(KillOldVersionThread);
        TerminateThread = false;
        Result = Delegate.BeginInvoke(null, null);
    }

    public static void Finish()
    {
        TerminateThread = true;
        Delegate.EndInvoke(Result);
    }

    private static void KillOldVersionThread()
    {
        while(!TerminateThread)
        {
            if(!IsOperatingSystemSupportingNow())
            {
                MessageBox.Show("現在実行中のオペレーティング システムはサポート期間を過ぎているため、動作を継続できません。", "致命的なエラー", MessageBoxButton.OK, MessageBoxImage.Hand);

                // 終了処理

                throw new Exception("Your operating system is not supported.");
            }

            Thread.Sleep(1000);
        }
    }

    private static Boolean IsOperatingSystemSupportingNow()
    {
        var Now = new DateTimeOffset(DateTime.Now);
        Int32 RequiredMajor, RequiredMinor, CurrentMajor, CurrentMinor;

        if(Now >= WindowsNT_5_2_End)
        {
            RequiredMajor = 6;
            RequiredMinor = 0;
        }
        else if(Now >= WindowsNT_5_1_End)
        {
            RequiredMajor = 5;
            RequiredMinor = 2;
        }
        else
        {
            RequiredMajor = 5;
            RequiredMinor = 1;
        }

        CurrentMajor = Math.Min(KernelVersion.ProductMajorPart, HardwareAbstractLayerVersion.ProductMajorPart);
        CurrentMinor = Math.Min(KernelVersion.ProductMinorPart, HardwareAbstractLayerVersion.ProductMinorPart);

        if(CurrentMajor < RequiredMajor)
        {
            return false;
        }

        if(CurrentMajor == RequiredMajor)
        {
            if(CurrentMinor < RequiredMinor)
            {
                return false;
            }
        }

        return true;
    }
}