This is one of my frequently used apps in Windows (Vista or XP actually) as it allow me to control which programs run at startup. Stuff like Adobe Acrobat always seem to install a few little programs in there which I'd rather not have so I can manually go through and streamline my bootup process - though this is less of a worry these days as I get used to Sleep mode in Vista.
To use it just type msconfig in to the search bar in Vista (or start, run, msconfig in XP). It required elevated privileges in Vista but also lets you do stuff like edit your boot config database and more. Tres handy
thanks to Tim for reminding me about this util.