Well, it took most of the night, but was finally able to replace the wireless network.
Part of the problem, which I still haven’t solved, resides in reconfiguring the ADSL router to run in bridge mode, and while I knew how it should operate in theory, the truth is that once configured, it would not connect me. There’s an automated app from my ISP that would reconfigure it, should I have the strange serial connector it uses handy, but alas, it’s one of those cables that I never remember where I put it. Fortunately, I can still connect on router mode, albeit only in outgoing direction.
The other part of the problem, was in getting WinXP to connect with WPA encryption. For the record, you need security update 815485 to be able to use it.
Oh well. While at first, I only got poor connectivity, suddenly there were 108Mbps of raw bandwith to do as I pleased. Nice!