Computer Won't Start After CPU Heatsink Reinstallation

Hello!

I built my computer about a week ago. I remember that it had a problem where it booted up (where Windows 7 started making the window, but never quite finished the "windows" logo) and then shut down again, to be followed by another try. I think I fixed it by pressing the "CMOS Clear" button. My temps were on the high side (36+ idle) so I decided to reapply thermal paste. I also added in another fan (connected to my fan controller). Now, when I boot up, I have the same problem. Pressing "CMOS Clear" doesn't fix it. I COULD boot from the Windows 7 CD/DVD. The changes I made:

- Reoriented the CPU heatsink
- Reapplied thermal paste
- Installed one 140mm fan

I decided to open up the case and see what was going on inside. So I unplugged EVERYTHING, opened up the side of the case, plugged in the power cord, and pressed the "on" button. Nothing. I pressed the "on" button in the motherboard. Nothing. I checked the power cord itself. It's fine. I tried switching the PSU to on/off. Still nothing. So now, I've got a computer that simply won't boot up. It won't start. No lights, no fans, nothing. The ONLY thing that was hot to the touch was the center of the CPU fan. The heatsink itself wasn't hot at all. Here is the build:

ASRock Z68 Extreme3 Gen3 motherboard
Silencer MK III 600W PSU (PC Power and Cooling)
i5-2500k
Hyper 212 evo
Fractal R3
2x4GB Corsair Vengeance DDR3-1600 CAS9 RAM
MSI R7850 Power Edition GPU

Please help! I think one of my parts may have blown out! How would I check what part it is? I don't have any other parts to switch out with.

Thanks!