Windows usage is mostly an occupational hazard for access to tools such as Microsoft Visio, VMware vSphere, proprietary VPN software, XenCenter, etc. We tend to use it on an as-needed basis via Parallels on macOS.
For a virtual machine with very little software, the assigned 60GB drive was full. Windows doesn’t display folder sizes in its File Explorer and so TreeSize Free proved a very useful tool for locating the space hogs.
This led me to a system and hidden directory:
\Windows\Installer. It had amassed 30GB or orphaned update files. 50% of my allocated space. To clear this up, PatchCleaner worked a charm.