Banks all over the world have known since 2007 that Microsoft would stop support for ATMs running Windows XP on April 8 of this year, but with that deadline looming, only one-third of those 2.2 million machines have upgraded their outdated software.

That means banks will be shelling out a pretty penny to Microsoft for continued support after the deadline, reports Reuters, unless they want a slog of malware and other glitches to hit their machines.

Microsoft admits that many banks have enlisted the company to provide extended support until all the ATMs are upgraded, but won’t say how much that’ll cost banks in extra costs, which were avoidable, of course.

“There are certainly large enterprise customers who haven’t finished their migrations yet and are purchasing custom support,” a spokesman for Microsoft said, without being specific as to which customers or how much money Microsoft will make off their dilly-dallying.

“The cost will depend on both the specific needs of the customer and what support they already have in place, so it’s different for every customer.”

To get an idea of the cost: At least five of Britain’s biggest banks have said they’re either negotiating for or have extended support, which could cost them each about $100 million, a London-based head of financial services advisory at a technology firm told Reuters.

He said the reason banks have left things to this late hour is likely due to all the new regulatory demands put in place in the aftermath of the 2008 financial crisis.

“They were probably not very serious about the directive that came in from Microsoft. There’s a lot of change going on at these banks at this moment in time and they would have seen Windows XP as one more change,” he said.

About 440,000 of those Windows XP ATMs are in the U.S. and many of those will still be running the outdated software after the deadline, said the vice president for risk management policy at the American Bankers Association. But because so many banks are in line to upgrade, Microsoft can’t get to all of them at once.

“There is a little bit of a bottle-neck,” he explained.

Among them is JPMorgan, with its 19,200 ATMs. It’ll start converting machines to Windows 7 in July, but hasn’t said how much it’s paying Microsoft for extended XP coverage.

Citigroup and Bank of America are also asking Microsoft for extended coverage, and are in various stages of the conversion process.

You can follow MBQ on Twitter and rest assured she’s not running on any outdated programs: @marybethquirk

Banks to be hit with Microsoft costs for running outdated ATMs [Reuters]

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