Red Hat

I have just recently got into using Linux RedHat 9. So far I love it, I have set it up on a server I am running. Right now I have set up Samba and am running a file server for my house. I have four computers, the linux box is connected to the internet through a switch I have. There are two NICS in the linux box, and I want one computer to gets its net connection through ther linux box. eth0 is connected to the internert, and eth1 is connected to my other computer with a crossover cable. The machine that is connected to the Linux box through eth1 does have access to my intranet. It can access files off the file server, but it will not connect to the internet or other windows shared folders on the network. My linux box is online and works fine, and it can connect to my other shared folders. Does anyone have any suggestion.
P.S. I dont know a ton about networking..just enough to set up a swtich and get my machines online..

If the machine behind the GNU/Linux box is not able to access the other boxes, then your not exactly able to access your Intranet.
Any reason you don't just connect all 4 machines to the switch?
What are you using for your router? How are the other 2 computers connected to the Internet?
Are you running NAT on the GNU/Linux box? Is the machine thats behind the GNU/Linux box using a static IP or being served via DHCP from the GNU/Linux box?
If you are using a static IP, you will need to set up the Gateway address under the machine behind the GNU/Linux box.
Is the GNU/Linux box using DHCP on eth0? eth1 or both?