Who are you? <smile>
Could be a variety of things and you are not the only one to suffer this, especially in COD4 (check the COD4 forums). I would try these things, in the following order, checking each time to see if it has solved your problem.
1. Completely uninstall Punk Buster and then reboot and re-install it. Get the installer fresh from here (
http://www.evenbalance.com/index.php?page=pbsetup.php). Many people are blaming PB as the cause for the dreaded 999 ping.
1b. Turn down some of the graphic features that COD4 is set up to (in other words go to OPTIMISE and use the settings the game recommends) and turn off the extra sound (where people can talk to one another in the game) as this overloads the sound buffers on all but the highest end cards)
2. Turn off Skype, especially the Skype Extras. You don't ever need the Skype Extras so shut that down permanently and then before playing COD4, manually Exit Skype from the tray.
3. Download Adware (free trial version) (
http://www.pcworld.com/downloads/file/fid,71307/description.html)run it and make sure there is no Adware/spyware gobbling up your resources.
4. Download the Standard version of Pingplotter (
http://www.pingplotter.com/download.html), you get 30 days to evaluate it and in that time, you or the more intelligent son of yours should be able to isolate the cause of high Ping
5. Try turning the firewall off (CONTROL PANEL/SECURITY) for the duration of a game (it is safe to do) and see if that helps
6. If none of those work, we will get into the Geeky stuff and alter Port Forwarding within your Modem to open a port specifically for COD4. But lets leave that for now until you have exhausted the above