Mark Russinovich: is Windows open or closed source?

Open source softwares typically are regarded by many as the only softwares that can be trusted when it comes to sensitive and must-be-secured environments, though the reality -at least the reality through what I see and read in the web!- tells us another story, it tells us for example that Windows is used in airports to manage flights all over the world and even warship hardware is equipped with Windows OS!
Bruce Schneier uses Windows operating system because it's easier for him to get the work done in a company that is Windows based, though he recommend not to use it for users and I believe this recommendation has to do with the bad history of Microsoft when it comes to security which had dramatically changed after the trustworthy computing initiative and the release of windows XP SP2 with an enabled built in firewall, not because of the closed nature of Windows operating systems.
Open source software is generally preferred because plus of it being free or at least cheap though Microsoft guys argue that its cost of ownership makes it more expensive than say Windows, its code is available to anyone, so there sure will be someone to review it ... presumably!
OK, I don't want to argue and chose open source over closed source or closed source over open source! I use both and I can live with that, But what I want to do today is introduce you -if you don't already know him- Mark Russinovich and show you some of the videos he appeared on explaining Windows internals in a simple and easy way to understand, with Mark, it doesn't matter that Windows is a closed source operating system, you get to see how the Windows OS works internally using tools he programmed himself! ... enough talking and allow me please to introduce you Mr. Mark Russinovich :

From Winternals to Microsoft, On Windows Security, Windows CoreArch.

On Working at Microsoft, Windows Server 2008 Kernel, MinWin vs ServerCore, HyperV, Application Virtualization

Mark Russinovich @ http://www.microsoft.com/emea/spotlight

To download Sysinternals tools: http://technet.microsoft.com/en-us/sysinternals/default.aspx

When Vint Cerf talks you should listen.

The Internet is full of information you can get to in a myriad of ways: texts, images, animations, sounds, videos, virtual environments (simulations), etc..., but no one has nor do will have time to go through all of this information to get what he or she needs even with the help of search engines and crawlers, so this is a challenge, therefor what can be done to circumvent it? well, as I am concerned I don't know for sure but still I've got a suggestion that I think is going to help you as an individual!
There is a saying that goes "To become a master, learn from the master", and what this saying conveys is exactly the suggestion for you to not get lost in the Internet jungle of links!

In this post and other ones, we will find out about some IT masters, and listen to them talk about technology they've created, innovated, or just explained in a simple manner to us to understand.

Now let us listen to Vint Cerf talking about the history of the Internet and the technologies it stands on :

Tracking the Internet into the 21st Century.

Internet Milestone - 30th Anniversary 3-Network Transmission.

San Francisco Engineering Open House, Keynote.

More videos on youtube.com and on video.google.com.