Tefler - I have some ideas and will check in tomorrow.
But as you are now online via the laptop and the router, albeit by wire, the isp address is probably not the problem.
I had to install my internet service providers (Telewest blueyonder) installation cd on to my laptop before it would work wirelessly.
Other ideas are - firewall could be blocking access.
Here is another link I want you to look at:
http://compnetworking.about.com/cs/windowsnetw orkin1/ht/renewipaddrwxp.htm
I'm sure all will be well when you've had a good sleep.
Goodnight for now.