The first computer I built was in 2001. I was 7 back then and I read shit loads of PC magazines back then, even thow I didn't know half the big words I knew enough to know what most parts did what. I built the machine and it worked like a charm, (although the boot times were slow due to some I/O error, can't remember). Was pretty beastly too, it had an Athlon XP 1900+ and a GeForce 2 Pro.
Anyways the point is that if had the basic knowledge back when I was 7 turning 8, then there's no excuse to fail at building a PC let alone someone who's supposed to be somewhat professional.