ZKS Offered Free By ISP

My cable internet is providing ZKS firewall and anti-virus protection for
free. It seems prudent to take them up on it. But having used this vast
resource before I wonder if any obvious pitfalls occur to the readers of
this newsgroup.
One conflict is going to be with my existing XP pro sp2 firewall, is it
going to be able to be disabled and stay that way? I am between anti-virus
programs at the moment which is why I have been reading the recent posts
here.
regards
craig