updated .net download link to point to 4.5.2

src/NzbDrone.Host/PlatformValidation.cs

@@ -11,6 +11,8 @@ namespace NzbDrone.Host
     {
         private static readonly Logger Logger =  NzbDroneLogger.GetLogger();
 
+        private const string DOWNLOAD_LINK = "http://www.microsoft.com/en-us/download/details.aspx?id=42643";
+
         public static bool IsValidate(IUserAlert userAlert)
         {
             if (OsInfo.IsMono)
@@ -20,15 +22,15 @@ namespace NzbDrone.Host
 
             if (!IsAssemblyAvailable("System.Web, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"))
             {
-                userAlert.Alert("It looks like you don't have full version of .NET Framework installed. You will now be directed the download page.");
+                userAlert.Alert("It looks like you don't have the correct version of .NET Framework installed. You will now be directed the download page.");
 
                 try
                 {
-                    Process.Start("http://www.microsoft.com/en-ca/download/details.aspx?id=30653");
+                    Process.Start(DOWNLOAD_LINK);
                 }
                 catch (Exception)
                 {
-                    userAlert.Alert("Oops. can't start default browser. Please visit http://www.microsoft.com/en-ca/download/details.aspx?id=30653 to download .NET Framework 4.5.");
+                    userAlert.Alert("Oops. Couldn't start your browser. Please visit http://www.microsoft.com/net to download the latest version of .NET Framework");
                 }
 
                 return false;