Ransomware: Windows XP. A patch available. NSA had the vulnerability identified. Huge problems in Asia and Russia; unless something happens today, interestingly US virtually untouched. Except for FedEx. Windows XP: released in 2001. Microsoft quit selling Windows XP licenses in 2008 except for netbooks (2010). XP's successor Windows Vista was generally panned by reviewers and users which probably slowed the "demise" of XP. Windows 7 finally overtook XP in total market share by the end of 2011.
Interestingly enough, according to wiki, as of November 2016, Windows XP desktop market share makes it the fourth most popular Windows version after Windows 7, Windows 10 and Windows 8.1. Windows XP is still very popular in some countries; Africa as a whole and in Asia, e.g. in China, with it running on one third of desktop computers (and highest ranked in North Korea).
Ah, yes, that big market for private computes: North Korea. LOL.