Well if it is for free then who cares if it fails after some time.
Just turn on the thermal protection in the bios and or software and do it! I would run the water through the existing tubing and run it into a res, then a seprate loop using the chilled water from the res to go through the computer system. Maybe even put a rad before it goes back into the res to keep the fountain working effeciently as the water would be cooler before it had to chill it.