[Tux_Fan]

There is no definate answer for how often you should defrag. It is like how often should i change strings. I would do it more often if you are constantly installing or removing stuff and less if your not. As far as optimization goes with Vista turn off anything you dont use. I would turn off automatic updates and only update occasionally followed immediately after by a defrag. Also if you are using the installation that was on your computer from the factory i would recommend reloading it because in most cases the factory puts a bunch of extra crap on as well.