By the way, here are some problems I've had in the last few years with components.
My ABIT BP-6 motherboard fried one day when I was changing over heatsinks on my two Celeron 400 cpus. I was careful about static and whatnot and the only thing I could figure out might have been the culprit is that the motherboard flexed a non-trivial amount from the pressure of hooking those metal clips from the heatsinks down onto the plastic cpu sockets, and a trace somewhere broke and the thing never worked again. Crap.
The onboard network controller of my 1 ghz Athlon system stopped working one day, causing a spontaneous system reboot, and that onboard networking never worked again. I went and bought a cheap 10/100 ethernet card and put it in and got it back online, but it was a bother doing it.
I had the onboard sound of another motherboard go out in the same way, by the way, and had to add a pci sound card to get sound working again on that machine.
A year after the onboard ethernet went bad the rest of the motherboard went titsup and I had to replace the whole motherboard. This was a Gigabyte brand motherboard.
A year and a half or so after building my Athlon64 3000 system in the spring of 2005 my Asus motherboard went bad. I actually got Asus to replace the motherboard under warranty (with a "refurbished", not brand new board) but it was a huge PITA dealing with them and I was offline with my main computer for several days. This Athlon64 3000 machine, btw, was the one I'm using now but upgraded to an AthlonX2 4400 cpu a year and a half or two years ago. Oh yeah, and I put the machine in a different case as well, and added three more hard drives, upgraded the video card, etc.
I had an eVGA video card go bad on me and get replaced under warranty.
I've had two power supplies go bad on me in the last few years. One of them was on my AthlonXP 2800 system that I turned off one Christmas vacation for about a week, and when I tried turning it back on when I returned home it simply never fired back up, and the power supply was tested and was certifiably dead. That wasn't my main box by that time so I let it sit for a while, then replaced the power supply and gave the machine to my wife along with a 22" Dell widescreen to replace her ages-old G4 iMac.
Oh yeah, I forgot to mention that the old Geforce 3 card on that system was flaking out and I replaced it with a newer but still cheap and good-enough-for-my-wife ATI card. She used that machine for another year or two and then the machine started experiencing random reboots. Recently the reboots had gotten pretty bad and it would often do it while she was still using it. I ran some tests to confirm that it wasn't the RAM that was bad, but that it was definitely a hardware issue. It had to be either the power supply, the motherboard, or the cpu. I replaced the power supply and the system still failed the tests (the OCCT tool and rebooting from a memory test cd and running the memtest), so I returned the power supply to Frys and bought the Dell. This is because it was either the cpu or the motherboard, and this was an ancient system by now and not worth trying to replace a 5 year old cpu and motherboard.
And what's my point? My point is that this kind of crap happens in the computer world nowadays, and not everyone knows how to, or is willing to, deal with it themselves. Since the OP has never done this before, obviously he's not really a hardware hound, and I'd really hesitate to recommend that a hardware non-enthusiast get into assembling their own machines from parts, because when trouble happens, they're going to be frustrated and be without their machines for a while.