When to pull the plug on old software. The evolution of digital technology can be ruthless in its speed. Not only does it give birth at a frightening rate; it has a nasty habit of killing its elderly relatives. Take the latest release of Apple's OS X operating system - Lion. This £21 Mac makeover adds more than 250 new features including an iPad-style app interface, wireless file sharing and a hugely expanded lexicon of finger-gnarling multi-touch gestures.