I cleaned out my fan and forgot which way it was facing. It now makes a noise from time to time. Before it was dusty, it was quite.

I have the Power Supply fan pointing down while the CPU fan is blowing counter clockwise. Meaning the air that blows from the PSU fan is getting caught with the current of the CPU fan.

I was told counter clockwise was the correct way, however. The PSU fan is blowing directly above the CPU fan.

This is how the majority of my computers is setup, out the box. The reason was the air that blows on to the CPU is cooling the heatsink.

However I was thinking the air from the PSU is going to heat up the CPU.

The computer is currently caseless. The original case has no where for the air to flow, asides the back.

use logic. it doesn't matter that much, just make it so the air flow is as good, uninterrupted, as it can be.

nintendo ftw!

He's not talking about a case fan...see thread title.

The CPU fan should blow on the heatsink.

actually it may not matter depending on the heatsink.
what heatsink is it?