Drivers ABI, being micro-kernel based, even if everything is kind of bundled together, subsystems talk over in-kernel RPC (LPC), nowadays drivers and critical kernel subsystems are sandboxed on their micro-vms, hyper-v is a type 1 hypervisor (Windows runs on top of it when enabled, is just another guest), many kernel subsystems have long adopted C++ (hence VC++ /kernel since Vista, and Windows Implementation Library, a set of C++ templates for kernel, driver and userspace resource management), async IO since Windows NT early days, COM as OOP ABI (even if tooling is somehow clunky), subsystems just like mainframe OSes,....