Well, I have personally never seen a heatsink and fan for onboard video alone... maybe nihil means the chipset???

I tried comparing the fan and chipset by size, but I really can't tell from the pictures ... So i'm just going to go down the list:

It can't be the cpu because you said it still has it's heatsink and fan...

I doubt it's your video card fan... If it has one...

So the only logical explination is one of the 2 chipsets... probably northbridge like you suspected... but, have you checked the case for any missing fans? The case will usually have atleast 1 fan....

It would help if we knew the make/model of the computer, or at least the motherboard.
I agree with nihil on this, it would be very helpful to know the model of the motherboard...

But everything else he said I have no clue what he means

***edit***

Btw, what part of chicago are you from, I'm also in the chicago area...