Airport-no external disk

Hi,I am using Mac OSX 10.5.8 and is connected to the internet with ethernet via Netgear WGR 614 v 9 which supplies wireless connection for my wife’s PC.I tried to set up a separate wireless network with Airport extreme so that I can connect wireless to another external hard disk with usb connection.I am not successful.In setting up I chose to make a new network and after saving the settings the problems encountered were no ethernet and no ip address.I ignored that and now the light is green.I cannot find the external hard disk,so I do not know if the network works or where to look for the disk.File sharing is on,with disk password ,guests can read and write and sharing over Wan.Thanks.