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 update to Windows XP SP1a. On September 9, 2002, Microsoft released Windows XP SP1. On February 3, 2003, Microsoft released SP1 again as SP1a. Windows Update will continue to offer the same set of updates for Windows XP-based computers that are running either SP1 or SP1a. Windows XP SP1a is the same as Windows XP SP1 except that the Microsoft virtual machine (VM) is removed in SP1a. Express Installation Most users choose the Express installation to update their personal computers. The download size varies, depending on how recently you have used the Windows Update online service. The typical 30-megabyte download will take approximately 90 minutes with a dial-up connection and a 56k modem, or 3-5 minutes with a broadband Internet connection. Network Installation The Network Installation download is 134 MB and ideal for IT professionals installing SP1a on multiple computers in an organization.