You can use tip 8200 » What are all the Group Policy settings, and what has been added for Windows XP SP2, to configure the Windows Firewall.
NOTE: If the Windows Firewall is NOT configured, when you start NetMeeting, you will need to press Unblock in the Windows Security Alert dialog that pops up.
If you wish to manually configure the Windows Firewall in Windows XP SP2 for the Remote Desktop Sharing feature of NetMeeting:
01. Start / Run / firewall.cpl / OK.
02. Select the Exceptions tab.
03. Press Add Program.
04. Press Browse.
05. Locate the %ProgramFiles%\NetMeedting folder, select conf.exe, press Open and OK.
06. Verify that the conf.exe box is checked.
07. Press Browse.
08. Locate the %SystemRoot%\System32 folder, select Mnmsrvc.exe, press Open and OK.
09. Verify that the Mnmsrvc.exe box is checked.
10. Press OK.