so I'm building a new compter and I have everything I need to build it. But I have one problem. I bought a 70mm fan that's suppose to go on the back of my computer case. I'm not sure if I really need this. I dont want the extra noise that this fan will create. Can someone tell me if I accually need this? (I'm not talking about the heat sink and fan for the proccessor, I'm talking about the fan that attaches to the back of the computer case)
I don't think that you need it .. you can work without it .. Fans are only for modding, not for performance or sound quantity
I would add the fan just in case you do have a problem,most of the time if you go into the bios setting there is the facility to see the temperature of the processor if it stays stable you could do without but usually the fans dont make much noise anyway and some m/boards can have a auto speed adjustment for increasing the speed if it requires it say on a hot day.Also make sure you put the fan on the right way so that it blows the hot air out instead of sucking all the dust in.Only a suggestion.
I'd use the fan, if possible you can also get adapters and or software to adjust the fan speed. Making it next to silent, yet still helping cool your system.
the fan is not needed just an addition for extra ventilation. Dependant on what the spec of the pc is you will be ok with the psu fan. I have one with an additional side fan and it does add a lot of extra noise. looks good with the led but the noise gets frustrating.
Either use the fan you have or if your concerned about the noise spend a bit more and get a quite fan.
You haven't given enough information to honestly answer this question. I most cases, you do need the extra airflow unless you are using some very low end, low power, low heat components or have additional cooling for the hot parts. Air flow is important to keep those parts cool, or you are going to have a big expensive doorstop.