The BIOS Companion highlights the uses of tons of BIOS Setup settings (even recommends settings for optimal performance), has a very complete section of troubleshooting related information such as error messages, beeps, and POST codes, and even includes 55 well written pages on several computer hardware topics.
The Hard Disk Database
The Hard Disk Database contains drive parameter settings for 1000's of hard drives, as well as information and jumper settings for controller cards and a number of other PC peripheral interface cards.
Communications and Networking for Windows
This book is a good reference for information on the Internet, modems, fax, software, managing a network, Netware, and plenty more.