forcifer

i think ultimate got it right, but as he said it is confusing. to make it a little bit less confusing, here is a jist:

the radiator cools down the coolant (water) to the coolest the RADIATOR and cool in the heat exchange time and to the coolest the external air temp is.

if to coolant is still warmer then how cool the radiator can get it, this little extra heat does not get pumped back into the system unless the coolant is hotter then what it is cooling (unlikely)

therefore, some energy is always being stored in the coolant itself, so the room will be a little bit cooler. until you turn your computer off, in which the extra heat of the coolant will slowly dissipate (i think its conduction, but i dont know) out into the air. however, by that time, the radiator will stop exchanging most heat so in the end, yes your room will be a little cooler, but nothing THAT noticeable (maybe a few C)