The registry, NTFS, the security model, and the enterprise tooling behind Microsoft's OS.
How WinRM and PowerShell Remoting turn scattered single-machine administration into fleet-wide scripted management across hundreds of servers.
How the Windows kernel represents processes as containers of handles and a security token, and the tools to inspect both live.
How the registry's hive files, keys, and value types work under the hood, and the tools to inspect and edit them safely.
How the Service Control Manager starts, stops, and supervises background processes, and how to configure and debug a service directly.
How Task Scheduler's triggers, actions, and conditions work together, and how to build and inspect scheduled tasks from the command line.
How WSL2 differs fundamentally from WSL1's syscall translation, running an actual Linux kernel in a lightweight, tightly-integrated VM.