Reading about how the US Navy <http://www.theregister.co.uk/2015/06/25/us_navy_windows_xp_support/> has signed a contract to get continuing support from Microsoft for Windows XP, led me to wonder how long is a “reasonable” interval for Microsoft to continue to provide patches and updates for this ancient OS. My reasoning is thus: Windows XP is still under copyright. Microsoft still considers it to be its “intellectual property”. The term “property” is deliberately used, to convey the idea of something owned by Microsoft, not by you, the customer. All you get when you buy it is a “licence”, not ownership. But with property rights come property responsibilities. If your property is causing harm or nuisance to others, the onus is on you to fix it. Therefore, Microsoft’s responsibilities over its “intellctual property” should continue just as long as it claims those property rights. If unmaintained Windows XP machines are being exploited as parts of botnets or spam relays or virus vectors or whatever, the onus for fixing those problems should be on the property owner, right? Under current US copyright law, that duration would be 90 years from when Windows XP was first published, or, by my reckoning, the year 2091.