Cleaning the hard drive

A couple of months ago I noticed that the performance on my personal laptop was not awesome. Deep in my soul resides a latent hardware geek who is always interested in getting the best performance possible out of the systems at hand.
I checked all of the basic things to see if there was some random service that was consuming all of the systems resources.
Overall, my system is rather healthy. My cpu is barely being used 25% of the time.
My memory is below 30% used.
My bottleneck is the hard-drive.
I need to upgrade to solid state drives, but that is a wee bit cost prohibitive, so I am tuning. Joy of joys!