Proxy Lan cards

Hello people.

I Got a two computers with two lan cards in both the systems.

One pc has got ubuntu linux and the other one has got windows xp.

I got leased line internet connectivity with static ip.

Now at present i want to connect this internet to my ubuntu linux for a time being?

and for windows xp for some time later.

Now how am i supposed to configure this static ip in my ubuntu and configure the other lan card for another network?

The same thing implies to my windows xp too.
Thanks for the answer.