Networking :: Set Up A Laptop As A Router To Connect Wirelessly To ADSL Router?

I have a desktop PC running Ubuntu 9.10 and Windows 7, and a Eee PC 701 laptop running EasyPeasy Ubuntu 9.04. I'd like to connect the desktop to the laptop with a wired connection (eth0), then the laptop to my ADSL router using wireless (ath0).

I have a crossover ethernet cable (I bought on ebay). I have set up my laptop with a static IP address on my LAN and it uses OpenDNS.

I have added this to /etc/sysctl.conf on the laptop:

net.ipv4.ip_forward=1

Then I tried this on the laptop:

sudo iptables --table nat --append POSTROUTING --out-interface ath0 -j MASQUERADE
sudo iptables --append FORWARD --in-interface eth0 -j ACCEPT

This is a variation on what I found on other sites describing how to set up a router. I don't understand iptables very well, but I gather that the above two lines should set up forwarding so that traffic from my router to the laptop will be forwarded to the desktop, and vice versa.

But this doesn't work. The connection doesn't even establish between the laptop and the desktop.