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The work that eventually became XP SP2 was originally supposed to be a new version of Windows. But the multiple security threats that had hammered Microsoft over the previous several years caused Microsoft to concentrate all work on security and de-emphasize changes in the user interface.
As Windows boss Jim Allchin later told Mary Jo Foley, the decision to make this a free service pack and not a paid upgrade was a deliberate attempt to maximize its adoption. Microsoft had seriously underestimated the security challenges that it would confront with Windows XP, and the improvements in SP2 really did make a difference.
For businesses, it offered much better administrative tools and deployment options than Windows 2000. For consumers, it included the Security Center shown here, which has continued to evolve to this day.
And it turned on the Windows Firewall by default, fixing the mistake that had been so helpful to earlier network-based worms.