As a former banker I can tell you that most ATMs run Windows NT 4.0.

However since the network is completely clamped down and the OS boots via network as well (no hard drives in ATMs), they are pretty secure.

I’ve also indeed seen some Windows XP terminals in use just lately - one in fact in a hospital my current company collaborates with - but it’s isolated and used to run some sequencer that was never ported to a 64 bit architecture, and apparently doesn’t run in compatibility mode either.