The one from PCWorld is actually a contemporary review for XP’s 25th anniversary.
Windows 8.1 is an odd beast. On the one hand it is like a service pack for Windows 8, and you could even upgrade it in-place through the Microsoft Store. On the other hand, Microsoft bumped the minor version number from 6.2 to 6.3, to make it look like a bigger change. No idea why someone would keep running the non-8.1 version, but maybe there are reasons. Some folks prefer XP SP2 to XP SP3. Apparently it works better on older systems.
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