Change requirements

- Running on Windows Vista or above

Signed-off-by: Syrone Wong <wong.syrone@gmail.com>

shadowsocks-csharp/Data/cn.txt

@@ -113,5 +113,6 @@ Failed to update registry=无法修改注册表
 System Proxy On: =系统代理已启用：
 Running: Port {0}=正在运行：端口 {0}
 Unexpected error, shadowsocks will exit. Please report to=非预期错误，Shadowsocks将退出。请提交此错误到
+Unsupported operating system, use Windows Vista at least.=不支持的操作系统版本，最低需求为Windows Vista。
 Proxy request failed=代理请求失败
 Proxy handshake failed=代理握手失败

shadowsocks-csharp/Program.cs

@@ -18,6 +18,14 @@ namespace Shadowsocks
         [STAThread]
         static void Main()
         {
+            // Check OS since we are using dual-mode socket
+            if (!Utils.IsWinVistaOrHigher())
+            {
+                MessageBox.Show(I18N.GetString("Unsupported operating system, use Windows Vista at least."),
+                "Shadowsocks Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
+                return;
+            }
+
             Utils.ReleaseMemory(true);
             using (Mutex mutex = new Mutex(false, "Global\\Shadowsocks_" + Application.StartupPath.GetHashCode()))
             {

shadowsocks-csharp/Util/Util.cs

@@ -157,6 +157,10 @@ namespace Shadowsocks.Util
             return userKey;
         }
 
+        public static bool IsWinVistaOrHigher() {
+            return Environment.OSVersion.Version.Major > 5;
+        }
+
         [DllImport("kernel32.dll")]
         [return: MarshalAs(UnmanagedType.Bool)]
         private static extern bool SetProcessWorkingSetSize(IntPtr process,