Hello to all and I hope someone can help

I have a Belkin ADSL modem/router which I had intended to use to set up a network using my static desktop PC and a Mac Laptop.

First time I tried I to set it up all seemed well but I could not connect to the internet.
Having looked at the router interface I thought that I had probably set up some info incorrectly.
Late at night couldn't be bothered starting again so left it for a couple of days.

Now.....

When I try to find the router interface, it is not there.

All the lights are on on the Router, however apparently I have "Limited or no connectivity"

When I enable the device it takes ages to try and find an ip address and when it does it starts with 165 (I recall - am not in front of my machine at present)

Have I done something so obviously stupid that I can't see it?

Sorry this is such a basic question but any help would be much appreciated.