I have just fallen foul of what turned out to be an old chestnut. The card produces a network connection which reports that the cable is unplugged.
I installed the client manager, which reported that the RF connection was fine, and the latest driver (which changed the layout of the dialogues wherein the WEP is entered, but was otherwise unsuccesful).
A google search showed that this is a very well known problem indeed, but it appears that not everyone has come across the answer. The answer is, actually, in a Dell knowledge base article, but not one that Dell's search utility was keen to reproduce. You need a 3rd bit of software to take the place of the cable between the radio modem and the pseudo ethernet port - it was true, the "cable" was not connected.
I ended up with 3 things to install. R22540, R43778, R46012.
The problem is with W2000 and the allocation of interrupts. The mini-pci slot is trying to use an interrupt that W2K can't allocate with a simple driver definition file.
I'm glad to have sorted it, but There have been hundreds of people inconvenienced by this in the past. They have gone up blind alleys with patching both the driver and hardware to sort ot things that should not have gone wrong in the first place. It took me at least 5 hours of hunting before I found it on the Dell web site, whose main points of entry assume you are using XP. I still don't understand why this code had to be downloaded separately. Anyway, I hope this helps other people.