I was curious as to whether I can make the fans run while the GPU,CPU, and hard disks are powered down. I want to do this to help cool down quickly without the components generating extra heat. is it possible to do this and if so how may it be done?
For what you want to do your only options are motherboard specific features. You will need to check the documentation of your motherboard or of the board you want to buy.
If you want the power supply to supply power to fans (or more common use for this trick, liquid cooling pumps) without powering the motherboard you can disconnect the power cables to the motherboard and use a wire to connect pin 14 (green) and any ground pin (black) on the ATX cable. This will turn thee power supply on and any attached fans or pumps with it.
Often this is done to prime liquid cooling systems when you are not sure yet if there are any leaks.
Pin out available here
Without some custom hardware hacking, no. When the system is in standby, only the 5 volt standby rail has power. The fans are driven via the 12v rail when the motherboard is fully powered. Of course, a modern CPU uses extremely little power when it is idle. Unfortunately, GPUs, at least from ATI, still burn power like it's going out of style when idle. You can put the hard drive into standby mode while the system is on to keep it from generating heat. In Linux this can be done with the