Although Microsoft officially stopped supporting Windows XP in April 2014, there are still plenty of people who are using it—and paying big bucks for the privilege.

According to the most recent statistics from Netmarketshare, more people finally are running Windows 8.1 than Windows XP: 13.12 percent compared with 11.98 percent. (Windows 8? 2.9 percent. And yes, 1.62 percent of users still run Vista.) Altogether, 44 percent of corporations still have Windows XP installed on at least one PC, according to CNN.

As you may recall, 29 percent of PC users were still running Windows XP as of December 2013, even though Microsoft had already announced the product’s end of life (and extended it, and extended it, and . . . ).

What finally got that 17 percent of people off the fence? Security concerns? Wanting to be up-to-date? An improving economy that allowed them to ditch the antiquated hardware that couldn’t run anything more modern than XP?

No, the consensus is that organizations are migrating from Windows XP because of Windows 10. In fact, 73 percent of enterprise users in a recent survey indicated that they intended to migrate to Windows 10 within two years, “which would make it the most rapidly deployed Microsoft operating system for businesses ever,” writes Leo Sun in the Motley Fool. Sixty percent of survey respondents said they had or were testing Windows 10, and 40 percent plan to roll out Windows 10 within its first year, writes Ken Hess in ZDNet’s Voice of IT.

What makes Windows 10 so appealing to enterprise users? “Windows 10 offers deeper mobile device management capabilities than its predecessors, which suits businesses with relaxed BYOD (bring your own device) rules,” writes Sun. “It also has beefier security features, like the biometric scanning ‘Windows Hello’ feature, which could reduce data breaches.”

In addition, because Windows 10 can be scaled across phones, tablets, and PCs, transitions between tablet and laptop modes should be smoother than between the Metro UI and the desktop in Windows 8, he writes.

But what does Windows XP have to do with Windows 10? With Windows 7 and 8—but not with Windows XP—Microsoft is offering a free upgrade to Windows 10. In fact, the survey found 55 percent cited the free upgrade as the Windows 10 feature that was most enticing to them, Hess writes—even though organizations with corporate Microsoft licenses might not be eligible for them.

“With Windows 7 no longer being sold brand new, the easiest way to secure a copy of Windows 10 right now is to buy Windows 8.1 and put up with it until the upgrade,” writes Rhiannon Nee in GeekSnack.

But some organizations unready to make the move are paying Microsoft to continue to provide them support. The U.S. Navy, for example, is paying $9 million for a Custom Service Agreement (CSA) to support about 100,000 PCs that haven’t been upgraded yet because they’re on ships and submarines out at sea, or because they support legacy applications that don’t yet work with more modern operating systems. (To put the figure in context, the Navy has a $150 billion budget, notes the Register. “The security patches are likely to cost little more than Navy expenditure on toilet rolls.”)

That said, the Navy may pay more before it’s through. “The Navy expects to upgrade its systems to a newer, nondefunct version of Windows by July 12, 2016, but it may take even longer,” writes Lauren Walker in Newsweek. “Contracts show the possibility of extending the agreement until June 8, 2017, which would raise the Navy’s bill to almost $31 million.”

And the Navy isn’t alone. “The Army recently approved a similar support agreement for its more than 8,000 devices still running Windows XP,” Walker writes. “Globally, almost 15 percent of personal computers continue to run the operating system, as do most ATMs.”

In addition, the Internal Revenue Service paid Microsoft to support 58,000 Windows XP systems in April 2014, writes Tom Jowitt in TechWeek Europe. The British government also isn’t immune. “A freedom of information (FoI) request by Citrix last autumn found that all NHS trusts were still using XP in some form, with 74 percent planning to migrate in March of this year,” he adds. “Another FoI request recently revealed that London’s Metropolitan Police Service (MPS) still has more than 35,000 systems on Windows XP.”

And CSAs are pricey, with a reported inflation rate of 50 percent a year, according to iTechPost.

The most popular operating system now? It’s still Windows 7, for which mainstream support ended in January and extended support runs out on January 14, 2020. Even though it’s been supplanted by Windows 8, its market share is still growing: 10 percent in the past year and 3 percent in the past month. In fact, in the past month it grew more than any other operating system, writes Mirza Umalr Balg in Tech News Today.

“People are still clutching to this ‘old favorite’ with traditional Start Menu and mouse / keyboard centric UI design,” agrees Mark Tyson in Hexus.net. The Windows 10 survey found 94 percent of respondents’ companies use Windows 7 as the dominant desktop OS, where it runs on 77 percent of the laptops and desktops, writes Hess.

“Windows 8, and 8.1 are yet to touch the 20 mark in the market,” notes Balg, adding that they’re unlikely to do so now given that Windows 10 is so close to shipping. And at this point, there’s no reason for Windows 7 users who intend to migrate to bother migrating to Windows 8 or 8.1 first.

This means the pressure is on for Windows 10. “If Windows 10 can’t attract a ponderous cut of the Windows 7 population, hundreds of millions of people will be marooned on an operating system that is anything but young,” writes Alex Wilhelm in TechCrunch.