Courses on Windows?

I'd like to learn more about the Windows operating system. I may not be a system engineer, but I want to learn about the inner workings of Windows and its parts interact. There are a lot of courses on the Internet that are free but I don't want to waste my time either.

1) What things should I look at when picking a course or individual lessons?
2) Does anyone have courses they can recommend?

So many of you have a great deal of knowledge and experience and I'm interested in what you have to say.