Lack of Daily Physical Access Doesn't Mean Safe for Windows
I've noticed in several different industries that run ATMs or PoS devices on Windows based systems that their administrators seem to perceive these devices differently, as they would a laptop. Evidently, they seem to regard them as considerably more secure because they are not physically accessible to ordinary people (I hope you know what I mean in the case of ATMs) or used for general purpose computing (at least, not supposed to be). Like a laptop, these systems need to be locked down, and they need to be protected by more than just a signature-based product using technology invented over a decade ago. Below are older posts that make the rest of my point:
http://www.blueridgenetworks.com/securitynowblog/endpoint_security/signature-based-antivirus-and-hips-technologies-poor-endpoint-protection
http://www.blueridgenetworks.com/securitynowblog/endpoint_security/secunia_report_signature-based_antivirus_misses_most_unknown_malware