Good article and worked for me

http://forum.codecall.net/tutorials/10175-how-set-up-nat-routing-windows-xp.html

http://www.ante.lv/xwiki/bin/view/Windows/WinXPRouting

http://www.nanodocumet.com/?p=14

netsh
pushd routing ip nat
uninstall
install
set global tcptimeoutmins=1440 udptimeoutmins=1 loglevel=ERROR
add interface name="NIC2" mode=FULL
add interface name="NIC1" mode=PRIVATE
popd

REGISTRY
HKEY_LM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\IPEnableRouter=1