I think we'll be keeping Win7 with the KB.

However, we've discovered in the PR that changing the default DLL lookup may cause Python to crash when accessing HKEY_PERFORMANCE_DATA (which fails to delay-load a DLL). This occurs because accessing that key enumerates a set of installed services (presumably both 1st and 3rd party) and one of those fails on AppVeyor. (The Azure Pipelines tests are fine, as are all the local test machines I've used.) There's no indication what AppVeyor has installed that is causing the problem.

So it seems we'll have to not use the safe DLL lookup for all parts of CPython, and restrict it only to ctypes and extension module loading. (Or else drop AppVeyor as a required check.)