I'm a developer - primarily .NET on Windows. I've recently started a new job which, although a senior dev role, is also requiring more Windows IT knowledge than I anticipated: domains, Active Directory, security, group policy, networking, etc. My knowledge of these areas was mostly acquired organically, and I feel I need to make it more systematic and fill-in the gaps.<p>So: what are some good dev-friendly knowledge sources in this area? I have a preference for books, but online is good too. And if you've faced this challenge, any tips on what worked for you?