If you really want to dive with both legs, I would look at MenuetOS . This is an operating system project written entirely in assembly language (for both 32-bit x86 and 64-bit x86-64 architectures).
According to the website, it has a graphical user interface, a TCP / IP stack, and some games, while still managing to fit on a single 1.44 MB diskette (remember these?).
The x86 release is open source, and the code is released under the GPL . (Unfortunately, it does not seem to have been updated since 2007, and the x64 version appears for closed source.)
Visit their website here: http://www.menuetos.net/
And download the source for Menuet32 here: http://www.menuetos.org/M32.htm
source share