Windows XP was the first version of Windows to bring together Microsoft's client and server product families. It became immensely popular after its 2001 release. This is all ancient history familiar to any regular TR reader. What you may not realize is that Windows XP is still immensely popular, despite being obsolete and unsupported for nearly two years.
Mainstream support for Windows XP ended in 2009, and Microsoft finally withdrew extended support—including security updates—in 2014. Two years later, between 7.3 and 10.9% of internet users world-wide are still running the aged operating system, depending on who you ask. That figure is higher than many other operating systems, including OS X and every flavor of Linux. In some regions, like mainland China, as much as a quarter of internet traffic still comes from Windows XP computers.
Running an outdated and unpatched operating system is a dire security scenario for an individual, never mind a business. According to Spiceworks' 2016 State of IT report, some 67% of North American businesses surveyed are still using Windows XP in some capacity despite that fact. That number is even larger outside of North America. Not bad for what ESET Security calls a "zombie" OS.
Given that upgrading from Windows XP likely means purchasing some new hardware, it's easy to understand why a large business might hesitate to upgrade. Even so, it's difficult to overstate the importance of moving on from unsupported software. For just one example, the 2011 hack of Sony's Playstation Network cost that company $171 million, and it may have been made possible via unpatched software.