I'd only consider running a hard drive cooler if-
-Your case has low air flow
-You're running more then three hard drives by eachother
-You have a hard drive that seems to run hot
-You have generally high ambient temps
If you were going to run a Hard Drive cooler, I'd look into one of these two-
1)
CoolerMaster CoolDrive Lite
2)
Evercool F117 NightHawk Hard Disk Drive Cooler
Personally, I'd get the first one. If you have open 5.25 bays that is.