For #1 add this to /etc/lilo.conf
Thats for windows on the first partition and be sure to run lilo from root.
Now for #2 Shorewall may have set-up iptables.Not sure where the script is for debian or Ubuntu
but it won't be hard to fix.
You should be able to flush any rules with
# iptables -F
# iptables -t nat -F
then you can try dhcp with