I own an Asus eee 900HA, running XP. I was expecting to find a hotkey sequence on the keyboard for turning on or off the built in webcam. There isn’t one. However, Asus provides a utility in the system tray (bottom right hand corner of desktop.)
You can download the User Guide from Asus, and it does contain this information.
Just right-click on the icon and you’ll see options to turn on or off the webcam, and options to turn on or off the wireless connection.