After cold start or on wake up a box appears saying "None of your preferred networks are available" then in the selection box is "dnbhouse" and sometimes an other entry.

What is this?
Is it important?
If not important, how can I stop this box from appearing?

Cheers

It's just showing you the current networks that are around at the moment. If you go and fiddle with AirPort settings in System Preferences that will fix it. Sorry I'm not able to give you the exact details, but I'm not 100% sure myself.

Hey mate, hope your enjoying the Mac experience

This is Leopard telling you that none of the wireless networks you have previously connected to are available. For example, I normally connect to 'Wilson Home' but if I go out to a new area and there are new connections around, it will tell me it cant find any old networks, but here are some new ones if you want to connect to them.

The names are just the names of other wireless networks around your computer (neighbors or whatever).

It sometimes might not find your preferred network on first try, you might need to give it a sec to scan again

Once you have connected to a network, it becomes a known network and it wont ask again to join it. I suppose its a security thing that it doesn't just automatically join new, unknown and potentially unsecure networks....by memory Windows used to just connect to whatever connection was strongest...

OK, thanks for the very quick replies.
I do not have any wireless networks. All I have is an Ethernet cable to my modem/router.

Can I then switch off/disable my wireless network and that will prevent the box appearing?

Ahhh ok, that would be why. You are picking up your neighbours wireless etc. Could be handy

If you use ethernet, best to turn wireless off all together. Go to right of the menu bar, find the icon with the cone shaped bars on it, click it and choose Turn Airport off. That should work

Thanks A.W - At work at the moment but will do so when I finished my night shift.

Thanks again all