I've had a quick look at a Windows 10 install and while there are still some .com files in there, they all appear to actually be the modern Portable Executable

I've had a quick look at a Windows 10 install and while there are still some .com files in there, they all appear to actually be the modern Portable Executable format. This makes sense given the old .com format was really just a binary blob that would be loaded into a single 64k memory segment. Keeping backwards compatibility for running them on modern 64bit processors would be difficult. At the same time Microsoft wouldn't want to break people's batch files if it can be avoided. By replacing the .com file's contents with logically equivalent code in a more modern executable format they can keep those batch files running without having to actually support legacy .com executable format. (note, that's all guesswork, Microsoft could have had a different reasons for doing it :) )