The last version of PM16 ended at PM18.1. A new program rebranded with the PrintMaster name entered the market a few years ago as PrintMaster 2.0 which has since been updated to 2011, then 2012 and most recently, 5.0.
Since PrintMaster 5.0, which was released about November of last year, can no longer be purchased either on amazon.com, broderbund.com or encore.com, looks like PrintMaster 5.0 was VERY short-lived.