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Windows 10 just turned one year old. Did you send it a card? No, me neither.

This edition of Microsoft’s operating system — newly improved with the “Anniversary Update” shipped Tuesday — has done a great deal to stand apart from its ancestors in that first year. But one thing it hasn’t done is displace them on as many PCs as Microsoft (MSFT) would like.

That’s a little disappointing. But it’s hard to blame Windows 10 for it.

The persistence of predecessors

Let’s start with Microsoft’s “Windows and Store trends” page for developers, which shows a steady increase in Win 10’s installed base. Still, as of April (the most recent month listed), Windows 10 was only on 40% of PCs in the US. Meanwhile, Windows 7 ran on 44% of the computers in the US as of April.

Worldwide, the numbers were even more lopsided: Win 10 at 30%, Win 7 at 51%.

That’s Windows 7 as in the release that shipped in October of 2009 and was appreciated most for not being Windows Vista. Microsoft replaced it almost four years ago with Windows 8 — although that release quickly reached a Vista level of unpopularity after its October 2012 release and now only runs on 15% of US PCs, according to those Microsoft stats.

But those figures only list versions from Win 7 onward. To get a fuller sense, turn to third-party sites that count browser and operating-system releases in use on the Web, and which record usage of older Windows releases as well as Macs.

StatCounter’s figures for July show that Windows 7 was the most popular operating system in the US, at 31.98%. Windows 10 was in second place, at 27.73%, and all versions of OS X ran on 17.52% of computers. Win 8 and its less-crummy upgrade Win 8.1 combined for 10.34% and Windows XP maintained its beyond-the-grave grip on 2.97% of computers.

The worldwide figures there and at NetMarketShare show Win 10 doing worse — only on 23.53% of computers in StatCounter’s numbers, 21.13% in NetMarketShare’s. The latter also has XP on a full 10.34% of machines worldwide, which should be a source of planetary shame at this point.

You could say that getting a new operating system on even a quarter of computers in a year ranks as a major achievement, considering that PC sales have been slumping overall and Windows users often wait until their next computer purchase to change operating systems.

But Windows 10 was also a free upgrade until July 29, when it began costing at least $120. Meanwhile, you can still buy new computers with Windows 7 pre-installed — the selection isn’t as good as what you could find in 2012, but you’ll still find a decent range at sites like HP (HPQ) and Best Buy (BBY).