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Windows & Linux home mini-network, iptables forward problem

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Windows & Linux home mini-network, iptables forward problem

Absolutely
1. Debian GNU/Linux, trying to configure as gateway firewall machine. Internet device is eth1, getting address using DHCP from ISP via 4-port router, OK. LAN device is eth0, configured with static IP address in 192.x.x.x range.

2. Windows XP SP2 to be client machine, eventually using DHCP to acquire network address via packets relayed through Debian machine on iptables FORWARD chains.

Problem: Although I can ping the Debian box's LAN card from Windows if I configure a static IP for it (not what I want to do, but a troubleshooting step), I cannot even ping the DHCP server address, so the Windows machine can get no IP address via DHCP. The FORWARD chain policy is set to ACCEPT for now, so I know it isn't the rules in the firewall script. But, I also have included the command
echo 1 > /proc/sys/net/ipv4/ip_forward
& called the modules
/sbin/depmod -a
/sbin/modprobe ip_conntrack_ftp
/sbin/modprobe ip_tables
/sbin/modprobe ip_conntrack
/sbin/modprobe iptable_filter
/sbin/modprobe iptable_mangle
/sbin/modprobe iptable_nat
/sbin/modprobe ipt_LOG
/sbin/modprobe ipt_limit
/sbin/modprobe ipt_state
/sbin/modprobe ipt_snat
/sbin/modprobe ipt_masquerade

in my script. The interfaces file is also OK, and they're all being raised on boot without error, but nothing is getting forwarded. I vaguely recall some unique setting in Linux that's necessary for internetworking with Windows but I can't remember what it is. I goof off with minor-league SQL and C# in the most advanced work I do in the office, and am not experienced with networking fundamentals, so don't worry about being condescending: I know that I'm a n00b with this question.

TIA

PS. The firewall rules that might be obstructing communication are allowing the Internet connection that I'm using to post this question, so I'm 51% sure that the problem is not with my iptables script. T-again-IA.