I have to do this at my home, because i run my website from my home server. I have an XP so if you have a different operating system then it's just a little different. It's all in the control panel, just the names are different.
Go to the PC with the internet you want to control
Go to your control panel.
Navigate to Network Connections
Click on the network that you are connected to. (this step is for XP)
Click Properties (Also XP)
There should be a list of things (if you are on win98, you might have to click on a tab. dont remember what its called though)
Click on "Internet Protocol (TCP/IP)"
(For win98, there are a few tabs you have to click on to do all of this, so try you best to do this right

IP Address: 192.168.200 (Make sure that in your router control panel you have your gateway set to 192.168.1.1 (if you know what you're doing, then you dont have to do that)
Subnet Mask: 255.255.255.0 (thats the one i seen used the most, choose which ever your router uses)
Default Gateway: 192.168.1.1 (Once again, make sure your routers default gateway is 192.168.1.1 too)
If these instructions aren't understandable, i will reexplain them better. i just didnt feel like typing a whole lot. if the internet stops working on the computer that you changed all these settings, you messed up somewhere.