I just built my first pc about 6 months ago and let me tell ya, the plugs only fit one way. it's that easy, with the help of all the wonderful people on here of course. The hardest part is sorting through the plethora of parts available, and picking exactly what you need,then finding it at the right price.
I built my entire machine from the keyboard to the monitor and everything in between for less than $700, comparable "branded" computers with comparable specs would be 1500 or so with keyboard,trackball,and monitor included. I agree with Tmagic, ecs is not good, I fried 4 power supplies before figuring out that my BRAND NEW board was a paperweight. (p4m800 I think, I try to forget). You can't go wrong with any of the Big name boards though and lot of times you can find processor/mobo combos for a substantial savings.