I've got bad experience with BitDefender - insane amount of crashes on win9x machines, and regular BSODs on HyperThreading capable machines running XP, problems with auto-update not being able to restart BitDefender after update, problems with not being able to shut down machines cleanly, etc...
It's antivirus capabilities seemed okay for regular purposes, but I'm not going to touch it again, ever - Kaspersky or NOD32 all the way from now on.
Windows XP has a built-in firewall since service pack 2, and you don't really need anything beyond that. If you're at the point where you need outgoing firewalling, you already have something bad on your system, and it's basically game over (yeah okay, if you're paranoid outgoing firewall means you can monitor apps... and either have the headache of setting up rules yourself, or have default rules that means security problems).
The XP firewall is fine enough for blocking you against incoming crap from the LAN, your NATing router will handle nasty stuff from the internet, whether you want KAV or NOD32 installed depends on your surfing habits, and besides that... well, SpyBot S&D if you use Internet Explorer.