Being self taught in the art of not burning the crap out of your computer, also known as PC maintenance, can be a slow and painful process. Too many blue screens of death can really get you worried about your rig, and repair shops will charge you a bucketload of cash just to defrag your drive for you. So, why not learn to do it yourself?
www.tweakguides.com
This site is run by an Austrailian chap named Koroush Ghazi, who has quite generously written several very useful guides on how to set up, maintain and get the most out of your hardware through tweaking. Using his Tweakguides Tweaking Companion for Windows XP, I have learned how to look after my PC properly. It has taught me to set up my machine the way that suits me, using tools and programs I didn't know existed, made my pc about 200-300% faster and less prone to crashes, and generally made maintenance an awful lot quicker and easier. I cannot heap enough praise on this guy and his guides.
He runs quite an extensive site, with many, many guides ranging from Gamers Display and Graphics (which teaches you exactly what the options in your gfx card actually do, from Vsync to Triple Buffering), to a Mozilla Firefox Tweak Guide (for streamlining your net browsing and making it faster). He does a guide for almost every major game in existence, from HL2 to Doom 3 to the Battlefield series. Trust me folks, this is not to be missed. Give the site a look, download the Tweaking Companion and see what it can do for you.