I have a 13" Macbook Pro (2010) which I share with my wife, mainly for surfing the net and checking email. No 3rd party software is even installed (except some tools like dropbox, 1password and xmarks). The macbook very frequently acts very slowly, making me suspect it's the hdd access. We get a lot of the well known rainbow ball too. I tried monitor activity monitor but nothing seems to stand out. Anyone got an idea what I can check?