public static string SystemCheck()
    {
        string Agent = HttpContext.Current.Request.ServerVariables["HTTP_USER_AGENT"];

        if (Agent.IndexOf("NT 4.0") > 0)
        {
            return "Windows NT ";
        }
        else if (Agent.IndexOf("NT 5.0") > 0 )
        {
            return "Windows 2000";
        }
        else if (Agent.IndexOf("NT 5.1") > 0 )
        {
            return "Windows XP";
        }
        else if (Agent.IndexOf("NT 5.2") > 0 )
        {
            return "Windows 2003";
        }
        else if (Agent.IndexOf("NT 6.0") > 0)
        {
            return "Windows Vista";
        }
        else if (Agent.IndexOf("WindowsCE") > 0)
        {
            return "Windows CE";
        }
        else if (Agent.IndexOf("NT") > 0)
        {
            return "Windows NT ";
        }
        else if (Agent.IndexOf("9x") > 0)
        {
            return "Windows ME";
        }
        else if (Agent.IndexOf("98") > 0)
        {
            return "Windows 98";
        }
        else if (Agent.IndexOf("95") > 0)
        {
            return "Windows 95";
        }
        else if (Agent.IndexOf("Win32") > 0)
        {
            return "Win32";
        }
        else if (Agent.IndexOf("Linux") > 0)
        {
            return "Linux";
        }
        else if (Agent.IndexOf("SunOS") > 0)
        {
            return "SunOS";
        }
        else if (Agent.IndexOf("Mac") > 0)
        {
            return "Mac";
        }
        else if (Agent.IndexOf("Linux") > 0)
        {
            return "Linux";
        }
        else if (Agent.IndexOf("Windows") > 0)
        {
            return "Windows";
        }
        return "unknow";
      
    }