The best replacement for xp sp3 is vista sp1.

The best alternatives to xp sp3 are rated as following:
★★★★★  vista sp1
★★★★  sp2
★★★  xp sp2
★★  vista sp2
★  windows vista sp1
  windows xp sp2

Your alternative for xp sp3 is not listed? Suggest!
Speaking about xp sp3, one probably shouldn't forget about ie8.

Other search terms related to xp sp3 and their ratings are:
★★★★★ ie8
You have in mind a companion for xp sp3 and it is not yet here? Propose!



Google Trends

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xp sp3
vista sp1
sp2