"Health care is one of the worst," said Silver, "simply because so many vertical market health care developers drag their feet so much."
The image of a hospital, doctor's office, even a dentist's, running an out-of-support operating system isn't reassuring.
Johnson was a bit more bullish on the chances of firms winning the race. "Yes, it's still possible," he said. But to pull it off in 18 months, an organization will have to dispense with an attritional strategy -- where only new machines are deployed with Windows 7 -- and tackle an everything-at-once chore.
Companies, or even consumers, who continue to think XP is "just good enough" to handle their computing needs can take steps, of course, to reduce some of the risk of running an out-of-date OS.
Gartner has a 10-item list it uses when it talks to clients who won't, or can't, leave XP.
"They have a number of choices, they can buy Custom Support from Microsoft, they can move applications that require XP to a Remote Desktop Services Server, they can segregate XP PCs on a separate network," said Silver, ticking off three.
Custom Support is the name of the after-retirement support plans Microsoft sells to businesses to cover some products, including Windows. Among the benefits of Custom Support: Microsoft continues to provide security updates graded as "critical" for a product, say XP, after it exits general support.
One tactic everyone can use, including consumers, is to switch browsers when XP falls off the support list.
"IE8 won't be supported [after April 2014] on Windows XP," Silver noted.
Because Microsoft has refused to support IE9 or the even newer IE10 on XP, when IE8 support ends, XP users will have to dump the latter to run a secured browser.
It's likely that other browser makers -- Google and Mozilla in particular -- will continue to support their Chrome and Firefox on XP up to and well past the 2014 cut-off. Mozilla, for example, dropped support for Apple's OS X Leopard, an OS that Apple itself abandoned in June 2011, only this month.
Also off the support list when XP retires: 2001's IE6 and 2006's IE7.
Gartner has that covered on its list as well, suggesting that enterprises who worry about in-house or third-party Web applications written for IE6 and IE7 move to Windows 7 -- where those browsers are not allowed -- but turn to a third-party product that lets customers run the creaky browsers on the newer OS.