| I wasted a lot of time before I figured out that 2 cards in one machine must be on 2 separate "networks", and that is set by the IP and the netmask. I agree with anomie that it will be easiest to get it set up with static IPs. No promises, but maybe:
ifconfig eth0 192.168.0.1 netmask 255.255.255.248
ifconfig eth1 192.168.0.9 netmask 255.255.255.248
The Windows machine connected to 192.168.0.1 can be set to 192.168.0.2 (or 3...7). The one connected to 192.168.0.9 can be set to 192.168.0.10 (or 11...15). Make sure that the Windows machines have default gateway set for the address they are connected to: either 192.168.0.1 or 192.168.0.9.
Each Windows machine should be able to ping the address they are connected to, and then you are ready to look at the Masquerading-Simple-HOWTO.
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/IMHO
//got nothin'
///this use to look better
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