Where is the hard drive in a Mac Book Pro 15" (early 2011)? This morning I am hearing an occasional periodic quiet clicking type noise from my macbook, from roughly the lower right quadrant, underneath the arrow keys.  I have no CD/DVD in the optical drive.   The noise repeats 5 to 10 times and then quits for a while, and it repeats at a regular rate of less than a second.

My question is: is that where my hard drive is?  If not, what is in that spot?
As you can see in iFixit's teardown, the hard drive is located in the lower right corner. The lower left is pretty much just the battery, which doesn't really have any mechanical parts that could make a clicking sort of noise.

Perhaps listen a little closer and see if you can isolate the noise better. I would also strongly recommend making regular backups if you don't already, as a clicking hard drive is not a good sound, if that is where it's coming from.