Generally speaking, past iterations of Windows allowed something of a free for all mentality in customizing images and Windows installations. It is worth noting that most of the techniques developed by IT professionals outside of Microsoft's walls were not truly supported by Microsoft. They however certainly achieved the goals of the IT professionals to customize the Windows installation for the required business use case. Usually, the solutions were stable (enough), and Microsoft provided best effort support when issues arose, so things were good.

As IT organizations in large enterprises matured, however, business folks became involved more in the IT process. ISO, Information Technology Infrastructure Library (ITIL), change review boards, procedures, and so on all came into the IT realm. At this point, the best effort and stable (enough) aspects of solutions became issues to address. One does not simply run global, enterprise-grade applications the world depends upon with kludged solutions hacked together from tips off various blogs and forums found around the internet.

To help IT organizations reduce support incidents, increase the stability of the solutions, and benefit the Windows platform, changes and recommendations started being made. In Windows XP, for example, it was common practice to swap hardware abstraction layers (HALs) based on CPU architecture so the organization could use a single image for deploying Windows. Microsoft never really supported this, but looking at the reasoning, the common issue was that Windows didn't handle this properly, so we hacked a solution to get around the issue. Therefore, making Windows not have the issue in the first place became a place to focus engineering resources on.

So came Windows 8.1 and then Windows 10--a conscious lock-down of the standard user areas of the operating system, isolation of the user experience, somewhat, to where they should be, to train users to not store things in C:\somepath but in the user profile for example, and also to train IT staff to image Windows in a reliable, repeatable method by creating the Microsoft Deployment Toolkit (MDT) and System Center Configuration Manager (SCCM). One can cite many such efforts by Microsoft to direct or push users and IT staff in the direction of a more secure, stable, or even supported position.

General guidelines for a successful implementation of Windows 10 are as follows:

Do not use the registry as a storage vehicle for large metadata
Do not use the registry improperly when developing in-house applications
Adhere to the least-rights concepts of Windows security