Recommended Minimum Protection:- XP SP2 + latest updates and the following software.
Firewall ZoneAlarm click here
Antivirus Avast4.6 click here
Antispy Spywareblaster click here + a2 click here
Remember to keep these updated or your wasting you time and PC resources.
These are obviously my preferences and work well for me with no conflicts, other members will have differnt preferences.