Finally got around to fixing this - turns out the cheapo DSL modem was not a router (despite the sticker saying so), thus my switch did not work.
And most of the login hints above did not let me access any settings that may be 'hidden'

So I added a Netgear FW/Router/Printserver I had leftover and configured it like my old system. Now all is set and her Wii, XBox etc are all wirelessly connected - with WPA2 encryption of course.

I think I was confused by being able to access the modem with 192.168.0.1 in a browser window. Ipconfig shows a 66.... address, so I should have seen right there that the modem was not a router... ah well... still lots to learn.

Thanks for all your assistance people !