I'm sure that's true (and Linux and Windows NT etc), but the headline and lede of this article strongly suggest that 95% of ATMs run a Windows OS that will be lose support next month. That's just not true.
(And frankly, I'd be a little suspect of any numbers sourced from a company in the business of upgrading old ATMs.)
This article http://www.theinquirer.net/inquirer/news/2334577/banks-negot... suggests that the problem lies (at least partly) with other bank computer systems which are running vanilla XP rather than the ATMs themselves which may be on XP Embedded, and that it is a substantial problem, with big UK banks apparently cutting special deals for extended support. EOLing WinXP seems to have turned out to be a nice little source of revenue for Microsoft...
(And frankly, I'd be a little suspect of any numbers sourced from a company in the business of upgrading old ATMs.)