Public Bank's ATM running Windows ?

I walked passing an ATM machine when I noticed something so familiar. I step back to the Public Bank's ATM and to my suprise .. it was a Windows desktop. The typical win 9x desktop. I'm not sure but it might be Windows NT. On the taskbar, I saw two minimized programs running which I guess the ATM's system. So the ATM system is just a normal windows application running in full screen. For so long I thought ATM machines were running under some specific OS, not the typical Windows. Or this only the case with Public Bank ? Anyone working in the banking industry should know about this. So what is the most used OS (for their ATM machines) among the local banks ?

I snapped a picture of the ATM machine with my phone's camera. Here it is - http://www.flickr.com/photos/k4ml/63230549/