Wkstn app searches intnt instead of local server -slows database a

Hi, I have 4 pcs running XP Pro SP2. One is used as server, the other 3 as
workstations. All hard wired to Linksys router with DHCP on. The pcs are
workgrouped without a domain. All pcs run a client-server app which has been
way too slow since installation. Software vendor says it is a network issue.
Ipconfig shows 'connection-specific dns suffix' and 'dns suffix search list'
of the ISP which is 'bc.hsia.telus.net'. For that reason I'm told, the
workstations get data from the server by going to the internet first to find
the server, instead of directly via LAN. How do I config this so the
workstations go directly via LAN? (All wkstns need to access the internet
too). Thanks ahead for your help. Ipconfig from the main pc shows:

Host Name: AlpineServer
Primary Dns Suffix:
Node Type: Hybrid
IP Routing Enabled: No
WINS Proxy Enabled: No
DNS Suffix Search List: bc.hsia.telus.net

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix: bc.hsia.telus.net
Description: Broadcom 440 x10/100 Integrated Controller
Physical Address: 00-0D-56-5D-A3-33
Dhcp Enabled: Yes
Autoconfiguration Enabled: Yes
IP Address: 192.168.1.101
Subnet Mask: 255.255.255.0
Default Gateway: 192.168.1.1
DHCP Server: 192.168.1.1
DNS Servers: 154.11.128.59
154.11.128.187