RE: Help! Network no longer recognizes AS/400 hostname

Ok, I'm learning much more about networking than I wanted to, but
unfortunately it is necessary.  If you don't mind, couple of more questions
before I sit down with the networking person:

First off, we are running DNS on a W2K server.

Second, just so I understand this correctly, having the address of the DNS
server on a particular computer allows that computer to resolve names, but
does not help other computers to resolve a name to this computer?  That is
the function of the DNS.

Next, how does the DNS server know all the names on the network?  Is there
an equivalent to the HOSTS file that should contain all the names?  Is this
maintained manually or by some automatic means?

Also, in going around trying the resolve the problems, I noticed that he had
setup most of the machines with the AS/400's IP address instead of the name,
which explains why some were having problems and others weren't.  Is there
an advantage one way or another?

Many thanks again for all your help!
Rick