If you are not running Windows XP SP1, install SP1a for security and reliability updates to the Windows XP family of operating systems. There is no benefit to installing SP1a if you are already running Windows XP SP1. We do not recommend that you install SP1a if you are already running SP1.

Note: Windows XP SP1a is almost identical to Windows XP SP1 except that the Microsoft virtual machine (VM) is removed in SP1a.

Technical Changes: Windows XP SP1a does not include or install the Microsoft VM, which provides support for running Java applets.

How to determine if you are running Windows XP SP1: From the Start menu right-click My Computer, and then clickProperties. If Service Pack 1 appears under System, you are already running Windows XP SP1.


  1. Click the Download button on this page to start the download, or choose a different language from the drop-down list and click Go.
  2. Do one of the following:
    • To start the installation immediately, click Open or Run this program from its current location.
    • To copy the download to your computer for installation at a later time, click Save or Save this program to disk.

Download Windows XP Service Pack 1a Express Install

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