Sync Centre. This is controls any and all devices that connect to the computer and syncronise content of any kind, whether media player, phone or PDA.
Most commonly, it's a replacement for ActiveSync. I'd love to show you it in action, but it doesn't recognise either a XDA IIi or a Vario II, and given that those are the only PDAs I have, AND a fairly broad representation of platforms between them, I'm going to conclude it isn't working just yet.