try these links...also you could do much worse than but Scott Mueller's 16th Edition of Upgrading and Repairing PC's. It's a little pricey but has all the information you will ever need to know - it also comes with a DVD with video clips plus load of other useful stuff.
Links:
http://www.buildyourown.org.uk/
http://www.buildeasypc.com/
http://www.daileyint.com/build/