The company also used the re-release as an opportunity to defend its software testing methods. It introduced new uses of "data and feedback" to improve its software quality, and uses extensive automated testing, external labs, partner vendors and 'self-hosting' (where development teams run their own software builds) as part of the testing process. It also tracked evidence to suggest quality was improving. Customer support chats and calls have been declining for much of Windows 10's lifetime, Microsoft said.

The problem, of course, is that this process still let a data loss bug slip through. Many of these testing method sare also familiar on some level -- self-hosting is usually called "dogfooding" and represents a common industry practice. These kind of serious update bugs tend to be rare, but it's not clear if there are any testing changes in place to reduce the chances of such a significant flaw popping up in the future.