DDJ Microprocessor Center(X86.ORG) (including links to download Intel processor manuals.)
Windows Driver and Hardware Development
Windows Programming
http://www.winprog.org/tutorial (in C)
http://webster.cs.ucr.edu/Page_win32/ (in Assembly)
PCGuide - Systems and Components Reference Guide
Main page
http://www.pcguide.com/ref/index.htm
Memory Layout Overview
http://www.pcguide.com/ref/ram/logic.htm
BIOS System Boot
http://www.pcguide.com/ref/mbsys/bios/boot.htm
Hard Disk Drive
http://www.pcguide.com/ref/hdd/index.htm
x86 Assembly Language FAQ
http://www2.dgsys.com/~raymoon/faq/masm.html#2
MASM Documentation
http://webster.cs.ucr.edu/Page_TechDocs/MASMDoc/index.html