• Forward these ports on your router (UDP I think, I left it as forwarding both services):
  • 28962
  • 44301
  • 45301

  This should fix the problem, go to the PB directory in the CoD4 install (C:\Program Files\Steam\steamapps\common\call of duty 4\PB by default) and run pbsetup.exe. Click ‘Update’ and see if you get an entry under ‘Client Version’ and ‘Server Version’. If not, try running pbsvc.exe and use the reinstall option. If that fails, manually reinstall PunkBuster.

• Manually reinstall PunkBuster.
  • Use ‘Add/Remove Programs’ for XP or ‘Programs and Features’ for Vista to uninstall PunkBuster and then restart to be safe (the dialog warns you some system files may not be removed unless you restart, this is Winblows after all).
  • Browse to the install directory for CoD4 and open the PunkBusters directory, usually C:\Program Files\Steam\steamapps\common\call of duty 4\PB .
  • Run pbsvc.exe or pbsetup.exe. I don’t recall which one I ran first, probably pbsetup.exe and then pbsvc.exe. Both install PunkBuster, pbsvc.exe checks PunkBuster and tests/(re)installs it, pbsetup.exe installs it and helps you manage games.
  • Run pbsetup.exe and click ‘Add a Game’. Select CoD4, it should automatically add the path. Click ‘Update’. PunkBuster should add entries under ‘Client Version’ and ‘Server Version’.

Let me know how this works for you.