MBP w/ OS X 10.8.3 Performing Quite Slowly Lately My MBP (2.66 GHz i7, 4GB RAM, 500GB HDD) is about two or so years old. It's been running like a champ for most of its life. However, within the past few months, I've noticed a considerable degradation in the speed and responsiveness of the computer as a whole.

I figured this might be a disk problem - so I ran the disk utility and it produced no noticeable improvement after a repair. Then I figured it might be a RAM usage problem - and I monitor and purge my RAM as often as I can (although I've not had to do this in the past). I figured it may be a problem with the system files, so I reinstalled OS X.

After all of that, the computer is still pretty slow. When I have only Chrome and iTunes running (with a handful of non-intensive small programs in addition), the computer will still operate at a snail's pace and use up almost all of its 4GB of RAM. 

I'm seemingly out of options to attempt to improve the performance of my computer to the level that it was about a year ago. Any help?
One of the first thing Apple technical support will have you do is to create a new user: log out of your current user, log into the new user and see if that helps. Toss a restart in as well.