When you run your second router with everything plugged into the lan ports it is a switch you are not using the router part. It will only route between wan and lan.
You must map the port in the main router to your laptop running ICS, then in the laptop in the ICS settings map it to the desktop. Your second router should not have any effect.
Will this work hard to say? ICS tends to be a huge problem to keep working correctly.
Other options which make life much easier.
1. buy cheap USB wireless cards for all your machines.. they are under $10 lately.
2. Use a wireless bridge/extender to connect between the main router and your "switch"
3. If your second router has wireless and can act a client use it as a bridge.
I live in a student house and i have 2 desktops and a laptop, all running windows, 2 xp and my main desktop running 7.
the laptop receives a wireless signal from our main router (which others in the house use), and through ics and another router shares the internet between the two desktops, on this router DCHP is turned off and the laptop is plugged into the LAN port.
my question is, i want to make my xp desktop into a game server, and this requires port forwarding...
i am thinking i should forward the ports to my laptop using the main router and then forward the ports from my laptop to the xp desktop using my router.
or should i just forward the ports directly to the xp desktop ip on both routers?
or something else..... i have tried the first and doesnt seem to work but theres a million other things it could be, just want to rule this out!
thanks for your time