Microsoft Office XP Service Pack 1 (also called Office XP SP1 and Office 10 SP-1) provides the latest updates to Microsoft Office XP. SP-1 contains significant security enhancements and stability and performance improvements. Some of the fixes included with SP-1 have been previously released as separate updates. This service pack combines them into one integrated package, and it includes a number of other changes designed to improve the reliability and performance of Office XP programs.
For more details, see this technical document at Microsoft
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