what are the procedures if some one want to build his own PC?
Research, first. Make sure you get a big enough case for a good motherboard, and make sure it comes with at least a 450w power supply, as you'll need something that big for a decent computer(if you're building, I assume it's for gaming, right?). Make sure your motherboard comes with a set of PCI, PCI Express, and PCI Express x16 slots, because you'll need those for modern day graphics cards. You'll want 3-4 gigs or RAM, more if you're using XP or Vista x64, as those will support more than 4. Make sure the cards are models known to run cool. And get at least a dual core processor. I got my first this past winter, and let me tell you, even at 1.6 ghz(I overclocked it since then) it has considerable advantage in performance over a higher, single core processor. Last but not least, get better cooling for the CPU than what comes stock. Something with a big fan and heat pipes. And setting up some fans in the case to create a good flow of air helps everything, too. One in front sucking in, one in back sucking out is generally sufficient.
Read a few back issues of Maximum PC magazine - they often have step by step instructions for building your oun PC. Have fun!
Here is a website I found that gives you step by step instructions: