Why on earth would you need a cooling fan for a hard drive??
Elevated temperature is one of the major killers of hard drives.
There are chips on the circuit card of the HD which get hot, and
high temps also can't be good for the armature and platter bearings.
In my Dell desktop, the primary HD is mounted right inside the
air intake holes of the case, positioned vertically with the circuit
card facing the intake holes and within an inch of the turbulent air
coming from the holes. The Dell designers could have reduced
the cost and design effort of the HD mounting hardware by mounting
it with the standard flat horizontal position with a single bent sheet
metal bracket, but they believed the added expense was worth it,
and in 9 years I haven't had a HD failure. That is just my personal
experience, but in the hardware NGs the professional system admins
and system assemblers agree that high temperature shortens the life
of a HD. Just take a look at the specs for any HD, and you'll see
the range of temps for safe operation. Those are given for a reason.
*TimDaniels*