Wireless Network - Windows Xp And Mac Os X


I have for several years been running a wireless network from my desktop xp machine to 2 xp laptops. All on an ad-hoc basis. My desktop is connected to the Internet via a separate wireless network which has been set up in my village. This is picked up via an Aeriel on the roof and piped in to my desktop via a USB connection. The point being that there is no Ethernet connection.

I have now purchased a new ibook which arrived last week. I also have an airport express station although I intended to use this for piping iTunes through my stereo.

So anyway, I have set up my ibook and it doesn't see my wireless network. Having read through various forums I expected to not be able to access the Internet via the ad-hoc set up - correct? However, I did expect to see the network. So question 1 -

1) Can I connect my iBook to my windows xp ad-hoc network and can I access the Internet through it. And if so how?

Expecting problems and to cut down on costs I have initiated getting broadband access via ADSL. This also comes with a BT Voyager 2100 Wireless ADSL Router. I haven't got this yet (problems with my phone line) but my second question is -

2) How should I best set up my PC's to network wirelessly? In particular should I connect my airport express to the router or should I just connect wirelessely from the iBook to the router? Which is easier / better and can you point me in the direction of instructions to guide me.

I have spent ages reading through this forum but am struggling to get answers to my particular problem.

Please help.