How do you prevent downloads from being run instead of saved in IE

HttpContext.Current.Response.Buffer = false;
HttpContext.Current.Response.ClearContent();
HttpContext.Current.Response.ClearHeaders();
HttpContext.Current.Response.AddHeader("Content-disposition", "attachment; filename=filename.exe");
HttpContext.Current.Response.AddHeader("Content-length", contentLength);
HttpContext.Current.Response.AddHeader("Content-Transfer-Encoding", "binary");
HttpContext.Current.Response.ContentType = "application/octet-stream";
HttpContext.Current.Response.TransmitFile(filePath);