Power one HD off?

I have two hard drives installed. For cooling purposes, I'd like to power off a second hard drive that I rarely ever use. Is this possible?

 

Technically, yes, it is possible. But if you rarely use the drive, it isn't generating that much heat. An idle hard drive usually runs at about 35c, which is not really that warm and is probably not doing much to increase temps in your system. Powering it off can only be accomplished by wiring in a switch to the power cable for that drive, and I personally think it's a really bad idea. If you're really worried about cooling, add an extra fan or two, or even add a dedicated drive cooler like this or if you have some empty CD drive bays, you can use something like this or this.
:cool

 

Please don't. Cutting the power to a spinning hard drive is the easiest way to scramble the contents.