Water Cooling

Having built my monster PC at the beginning of the year, and having listened to the monster electric blue fan ever since I'm now looking at watercooling to completely silence the whole shabang.
So, what I want to know is:
What aside from the processor and GPU are major sources of heat in a pc?
Is it possible to remove the fan from the GPU and watercool that as well?
And what do HDD's need by way of cooling?
So, what I want to know is:
What aside from the processor and GPU are major sources of heat in a pc?
Is it possible to remove the fan from the GPU and watercool that as well?
And what do HDD's need by way of cooling?