Close ports in Windows XP / 2000

Hey all

Just a quirky one, I am running a 2000 advanced server (with ISA and all the goodies) and I have about 20 or so XP clients and 10 or so 2000 clients. What my port scans have shown is a great number of “dodgy” open ports on some of the xp machines and even on the ISA server itself 🙁

I have blocked access to theese ports using ISA and have since been bombarded (in the ISA logs) by authorisation failures…

What I would like to know is can you close open ports (within windows xp and 2000) that “dodgy” applications may have opened? Better yet does anyone know of any Active Directory settings that could help in this situation