Why should you care about this update ? If you ever encountered performance issues running AJAX applications (e.g. Gmail), you should absolutely consider installing this update. This update includes an updated Garbage Collector that used to previously make AJAX appliications run pretty poorly. This update is available on Vista and we are now providing this to all supported OS versions (XP, Win2K, Win2K Server). You will see noticeably better performance on your favorite AJAX applications and with more and more AJAX applications coming on line, you will be very happy you did this.