Can't get past internet set up page.

I have just reinstalled OSX on my 20" White iMac 4 intel as I'm planning to sell it. Once the reinstallation process was complete,

I selected United Kingdom for the region I am in on the welcome page.

I then selected 'Do not transfer my information' on the 'Do You Already Own A Mac' page.

I then chose 'British' on the 'Select Your Keyboard' page.

I then selected 'Airport wireless' on the 'How Do You Connect' page.

I then select my listed wireless network on the 'Select A Wireless Service' page, put in my password and clicked continue.

I then get an Airport error box pop up that says there was an error joining the selected network, I click ok but am stuck on this page,

All I can do is click back to the previous pages.

Please help!