Microsoft has released a new Windows XP Service Pack 1a as a Network Install for IT Professionals, a Checked Network Install for IT Professionals, and an Express Install (32-Bit) for End Users. Thanks File Flash. Here's the deal, which seems to indicate this is not required if you already have Service Pack 1: "Windows XP Service Pack 1a (SP1a) provides the latest security and reliability updates to the Windows XP family of operating systems, and includes Internet Explorer 6 SP1a. Windows XP SP1a is designed to ensure Windows XP platform compatibility with newly released software and hardware, and includes updates that resolve issues discovered by customers or by Microsoft's internal testing team. To determine whether to install Windows XP SP1a, we recommend reviewing the Windows XP documentation and information below. If you have already installed Windows XP SP1, you do not need to Windows XP SP1a."