Microsoft wants Windows XP users to rely on Windows Messenger for communicating on the Internet. If you used NetMeeting in the past, you're supposed to switch to Windows Messenger.
NetMeeting is still in XP, however. It's just hidden. If you want to use NetMeeting, here's how you can open it:
Click on the Start menu.
Type "conf" in the Command box and hit OK.
NetMeeting will launch. You'll have to go through the setup Wizard the first time you launch it. After that, it's just like old times.