hey orestes1984, before you have a definitive answer with zero knowledge of the subject, look and search around first before you chime in.
OP, in late 2004 going into 2005 Apple started silkscreening a triangle liquid cooling warning symbol on the top of the metal cover that is the spacer lid to the powersupply, and in most regions of the world put a yellow warning sticker on the clear air dam deflector that said something along the lines of "Warning system contains advanced liquid cooling system, in the event of a leak if you see dripping unplug and power off and refer to manual" in which the manual says call Apple and take it in for a repair.
I have a early 2005 dual 2.3 which is air cooled, yet it has the warning print on the top of the power supply cover,I also have liquid cooled dual 2.7's with no warnings anywhere. and I've seen spare air dams with the sticker, I think Apple just used what they had on hand for those 2 parts, which happened to have Liquid Electroshock warnings on them.
The easiest way to tell is by your CPU speed, the Dual 2.5 (june 2004), the Dual 2.7 (early 2005), and the Quad 2.5 (late 2005) are the only models that have any liquid cooling system in them. I'll have find the pictures but its easy the heatsink is either a radiator (like a car) or a stack of cooling fins/sheets.
