DigitalHermit

REMINDER: this thread is not to ask questions about your PC. Please create a NEW thread if you still have issues after going through this thread.
 
So, you've put together your brand new, shining rig. You plug in the power cord and push the button. Nothing happens. What now? The answer depends on what is happening:
 
 
The machine doesn't do anything. No beeps, LEDs or spinning fans.
Check if your power cable is firmly plugged in on both ends (you would be surprised how many issues this resolves) Check if the power supply (PSU) has a button to cut the power to the machine. Check if this button is in the position denoted with ON or I Check if EVERY power cable is plugged in securely, reseat if necessary. Check if the power button is installed correctly (consult your motherboard manual) Try shorting out the pins you connect the power button to manually. If this powers on your system, you have a faulty power button. Check with a device of which you know that it works if the power outlet you're using is actually providing power. If this hasn't solved the problem, check if your PSU isn't dead. To do this, you can follow these steps:
Unplug your power cord and/or flip the switch on the back of the PSU in the position denoted with OFF or 0 Unplug every connector coming from your PSU (this is very important) Using a bent paperclip, short out the green wire on the 24 pin header with any of the black wires, like so. If you have a PSU that shuts down its fan under low load, or a PSU that is fanless, connect something small like a hard drive to it. Plug in your power cord and/or flip the switch on the back of the PSU in the position denoted with ON or I If the PSU does NOT power on (the fan/hard drive you connected should start spinning) after following these steps, your PSU is in all likelyhood defective. Request an RMA.
If the PSU DOES power on, then the problem is most likely your motherboard.
 
 
The machine does power up, but my screen remains black (no POST).
Make sure your BIOS version is compatible with the CPU generation you're trying to run in your motherboard, you can consult the manual or the manufacturer's website about this. Check if EVERY power cable is connected. Auxiliary power connectors included. Make sure the cable coming from your monitor is attached securely to the graphics card. Also make sure it is securely attached to the monitor itself. Make sure your PSU is powerful enough to power your complete system. Try booting the system with only a monitor but no other peripherals connected. (Thanks @Steven Schaefer) Make sure your monitor works by testing it on a different computer. If you have both a dedicated GPU and an iGPU, try your monitor on both the outputs on the graphics cards as well as on the motherboard. When trying the iGPU, if the board has VGA out, try that too instead of just digital out. (Discovered by @evening) Make sure all connectors and cables are plugged in securely, reseat if necessary. Make sure your RAM, CPU and GPU are plugged in securely, reseat if necessary. Remove riser cables between GPU and motherboard. If this solves the issue, try lowering your PCIe version/speed in the bios to PCIe 3 or lower (Thanks @problemsolver) If the motherboard you're using has debug LEDs, check the error code and consult the motherboard manual to see what it means. If you have a debug speaker connected to the motherboard, note the beep sequence and consult the motherboard manual or this thread to see what it means. Try clearing your CMOS. Try booting your computer with only a motherboard, CPU and one stick of RAM attached (if you don't have an iGPU, plug in your GPU as well 😉 ). Make sure your GPU works (if you have a dedicated one), try it in another computer. Make sure your RAM works, try it another computer. Make sure the RAM is compatible with your CPU and your motherboard.  
If the PC still doesn't POST after this, create a new thread and, as explained here, post IN FULL DETAIL about your problem. Make sure you include the following:
System configuration Troubleshooting steps you already did Any additional information that may be relevant.  
Lastly, if you find any mistakes/grammatical errors, inaccuracies or missing steps in this post, please do post them in a comment so I can fix it.
 
 
PS: @TheXDS has posted how you can do some more in depth checking of the internal circuitry of you PSU. The only thing you need is a multimeter or potentiometer (if you're oldschool :D). You can find his post at http://linustechtips.com/main/topic/42440-readme-how-to-respond-to-a-no-post-or-no-power-up-situation/?p=4561958

Ah my bad, I thought the question was for buiding a cool system. As far as keeping an existing system cool the only real thing you can do is change the location of where the pc sits and how fast your fan speeds are. Something else a little more extreme is buying high quality thermal paste and replacing the existing paste you have on your cpu and gpu but that might not help much. 

http://www.digitaltrends.com/computing/intel-enthusiasts-devils-canyon-pc-cpu/#!8Yh47
 
Earlier this year, Intel made waves with PC enthusiasts by announcing the arrival of new “Devil’s Canyon” chips. Aside from a cool code name, these processors were said to provide vastly improved overclocking potential, thanks to re-worked power management, and a thermal interface polymer that conducts heat more efficiently. Now that they’ve arrived, however, enthusiasts are wondering if they were duped.
Fool me onceBefore talking about Devil’s Canyon, though, let’s first remember what led up to it. The release of Haswell last year was expected to provide a modest, but noticeable bump in performance over the previous generation.
Once reviewers laid their hands on Haswell chips, however, it became clear that something had gone wrong. The new 4th-gen desktop processors were only 10 percent quicker than their predecessors, at most, and they were priced slightly higher than their 3rd-gen equivalents, which meant their value was questionable.

Worse, the 4th-gen chips switched to a less effective thermal material, which made them less suitable for overclocking. Reviewers noted that the new processors often peaked at a lower overclock speed than those that came before. The Tech Report, for example, managed to achieve 4.9 GHz with an Ivy Bridge chip, but only hit 4.7 GHz with the Core i7-4770K. Tom’s Hardware, meanwhile, only hit 4.6 GHz with a single 4770K; most maxed out at 4.4 GHz.
This development is only the latest in a long line of decisions that has put Intel at odds with die-hard PC fans. In 2010, the company eliminated the ability to overclock most chips by tying the speed of every chipset bus to a sole internal clock. Intel then poured salt on the wound by introducing expensive “K-series” processors that do have an unlocked multiplier, but also cost more than their locked siblings.

Fool me twice
Intel’s execution of its anti-overclocking campaign was made with few excuses. Enthusiasts often felt ignored, but they also had little choice but to stick with Intel. AMD’s latest processors simply aren’t quick enough to compete.
So it’s no wonder the community perked up when Intel’s VP of the PC Client Group, Lisa Graff, began hyping the new Devil’s Canyon hardware. Marketed from the beginning as an answer to enthusiasts who felt ignored, the unlocked chips promised maximum speeds of up to 5 GHz on air cooling, a truly outstanding figure. Enthusiasts went starry-eyed and light-headed as they dreamed of what might be possible. Overclocking quotes from manufacturers are usually conservative, after all; if Intel says 5 GHz, then what’s really possible?

Less than 5GHz, as it turns out. Numerous reviewers have found that the new Devil’s Canyon chips are barely better than the Core i7-4770K. HardOCP, PC Perspective and The Tech Report all maxed it out to 4.7 GHz, and even that figure did not come easily. The Tech Report even noticed the new Devil’s Canyon 4790K CPU required more voltage than the 4770K to achieve the same clock speed. A few extreme overclockers have managed better results (the record is 7 GHz), but only by disabling two cores and using liquid nitrogen for cooling. That, of course, isn’t practical for 99.9999999 percent of owners.
Even the new unlocked Pentium processor should be viewed with skepticism. Yes, it’s a $75 processor that some reviewers have overclocked as high as 4.5 GHz, but it’s also a dual-core without hyperthreading, and you’ll want a Z87 or Z97 motherboard to make the most of its potential. In short, you’ll be spending $175 to $200 on a processor and motherboard combination that stumbles whenever it’s asked to handle a workload with more than two threads – and many demanding applications, including the latest games, will ask for more than that
 

Steps:
1) take note of error code and beeps.(you did!)
2)find the jumper(or sometimes button) and clear CMOS. 
 
It should boot now. Something in the BIOS is not letting it boot. Clearing the CMOS will reset to a safe default.

Actually, yes it can limit it. Heres how-
if the psu is unable to give high enough or stable enough power, you graphics card will likely be stuck on low power mode, it wont ramp up to full clock. Remember, some GPUs used to even run wihtout the power connected and would either not go from low power mode or would even game for a while until an eventual bluescreen using just the power provided over PCIe. If a power supply is giving a weak wattage, this can happen as well. 
So the power supply is worth checking, as well as the GPU. Swap the power supply. Test the gpu on a different tower or monitor the clock and usage using GPU-z. 
I've actuaolly blown a power supply partially like this before by kicking a cheap power strip in the switch by accident. I don't know how it works, but it must send brown power or something. Oddly enough it was also a corsair power supply. Melted the 12v pin. Luckily the components were fine. 

what the hell? where do you live that the ambient temp is like 5C?