TweakGuides Tweaking Companion
 

The TweakGuides Tweaking Companion (TGTC) is the complete system optimization guide for Windows users. Designed for novice and advanced users alike, it is written in plain English to help you genuinely understand and optimize all aspects of Windows and your PC. The latest versions of the TGTC are available for both Windows XP and Windows Vista, and the Regular Edition PDF can be downloaded completely free of charge.

http://www.tweakguides.com/TGTC.html