Dynamic DNS

I have a dynamic DNS that a friend of mine set up for me a few years
ago. Unfortunately, my friend passed away, and I have been unable to
find any resources for modifying the IP information contained within.

The system is FC 4, and is running very well - however I have migrated
the site that uses the dynamic system from one server to another.
While I have been able to determine how to change the www. subdomain,
I have yet to be able to change the IP for the domain root.

So, if I type:

$ host www.foo.com

I will receive a reply like:
www.foo.com has address 192.168.2.100

BUT, if I type:


$ host foo.com

I will receive a reply like:

foo.com has address 192.168.2.45

The file that appears to manage this domain is in the format
foo.com.jnl

Is anyone familar with how to modify such an entry? I'm sorry for
being vague if I am, but this one has me more than stumped. Changing
the www was a challenge enough.

Thanks!