Server OS Spotlight --http://www.serverwatch.com/server-topics/index.php/28741/Server-OS-Spotlight.htm
The server operating system is the engine behind the applications running on the server. Whether you choose Windows Server 2008 R2, Ubuntu server or a proprietary Unix server, it's important to know what's under the hood. Keep up with the latest news and trends, and find some tips to give your server a tune-up, here.
The FreeDOS Project --http://www.freedos.org
FreeDOS is a complete, free, 100% MS-DOS compatible operating system. Works on old hardware, in DOS emulators, and in embedded systems.