Hello Prasads racha,
if the Linux machine is always connected and has two NIC you can configure you WinXP clients to use that machine as gateway to the internet.
That’s to say:
NIC 1 = 10.10.1.1 (connected to the internet)
NIC 2 = 192.168.0.1 (connected to LAN)
The workgroup will be 192.168.x.x with subnet 255.255.255.0 and gateway 192.168.0.1
If you have DNS installed on the Linux machine thean you can add 192.168.0.1 as DNS for the workgroup computers; if you don’t have DNS installed you can use the ISP DNS servers for the client computers.
Remember that on the Linux machine routing must be configured correclty; I ignore which distro you are using but most of the latest distro provide guided network sharing so follow the steps in order to have everything configured the best way possible.
P.S. Having the Linux machine with two NICs allowas you to implement firewalling, DMZ, proxy and many services that you can use to allow/disallow to the internal NIC.