Product overview:
http://msdn.microsoft.com/embedded/getstart/devplat/pos/default.aspx

Order an evaluation version:
http://msdn.microsoft.com/embedded/getstart/evaluate/default.aspx

Windows Embedded for Point of Service Installation Guide:
http://msdn.microsoft.com/library/en-us/wpossetup/htm/hardwarerequirementsforwindowsembeddedforpointofse.asp

The mp3 interview can be found here - the XML file has also been updated (from Mike Hall's blog).