windows 98 user can not access the shared folder on windows 2003 s

Hi, everyone,
Previously my customer running Windows NT Server as DC and file printer
server, recently we build a new 2003 sbs server as DC and file and printer
server, and the 2003 server also serve as DNS, DHCP. WINS not installed ,
but was installed on the NT server, so now the NT server only act as a POP3
mail server.
The problem is sometimes, some windows 98 or 98 SEC can not see the network,
can ping to the server, however, can not find from network place, even failed
if search the server. show can not find, or sometimes, can see the server, if
click, will got err msg of "network is not accessable", even at this stage,
can use the pc access internet. seemed only can not find company network. the
after restart the windows 98 pc, everything is fine.

I have few questiones on this:
1. I do think there is something wrong on the TCP/IP setting on the windows
98 client. but don't know how to correctly. such as:
shall I enable DNS, WINS, or Select use DHCP to resolve?
2. previously in NT server enironment, they configured disable DNS, use
wins, and some 98 pc set Using DHCP to resolve, now the domain server is
2003, need we do some changes on the windows 98 pc?
3. When need use WINS to resolve?

Thanks for any suggestion on this!

Rgds
Shermaine