Here are some useful gaming technology and history links... 

MDX (Managed Direct X)

http://www.mdxinfo.com/tutorials/primer.php

 

Wikipedia articles on directx and direct3d

http://en.wikipedia.org/wiki/Directx

http://en.wikipedia.org/wiki/Direct3D

 

XACT

http://msdn.microsoft.com/library/en-us/directx9_c/xact_wggt_intro.asp?frame=true

 

XINPUT

http://msdn.microsoft.com/library/en-us/directx9_c/dx9_xinput_xinput_dinput.asp?frame=true

Fixed function versus programmable pipeline

http://news.com.com/An+inside+look+at+Windows+Vista+-+page+4/2100-1043_3-6051736-4.html?tag=st.num

XBOX Creator’s Club press release

http://www.microsoft.com/presspass/press/2006/aug06/08-13XNAGameStudioPR.mspx

 

Also, if you launch the DirectX texture tool, you can open up TGA files.