|3.5" drives require either an eternal power source or a USB 'Y' cord so it can draw power from two USB ports. Some newer motherboards support a higher current draw over USB 2.0 ports, but older boards do not and the original USB 2.0 specs do not cover the higher current these drives require. On that drive, purchase a USB 'Y' connector intended to draw additional current from the second USB port only that is made for external drives, or look to see if there is a port for an external power source.|
I do not know if Firewire supports this or not, though Googling might get the answer.
We have a number of 2.5" external drives in the family, some came with USB 'Y' plugs to ensure enough power, some of the newer ones did not (USB 3.0 ones). None of them have fans, None gets more than a little bit warm.
A drive purchased used, should be tested with the manufacturer's test utility before trusting it with important data. While on the idea of important data, portable drives are fine for backing up files from a computer, but is you are using it for additional storage space, make sure there is a copy of those files some where else for security (one drop or improperly unplugging it can make it unusable).
You have to be a little bit crazy to keep you from going insane.