Not that much help, we haven't got it fixed yet !
Now I'm somewhat confused by mention of Atheros; this is a different chipset manufacturer altogether. My T42 for example could have been suppled with either Intel *or* Atheros wireless cards, so in its original config I guess the driver sets for both might have been available with all the "recovery" software. IBM calls the packages (driver plus Proset) wlanint or wlanath. BUT my particular machine has the Intel2200 chipset card so I need to use the Intel driver *and* can use Intel Proset management software.
But you said the machine has the Intel 3945 - you know this because a) you've physically seen the card, b) you've looked at the product specs for the machine (and the card hasn't been swapped out) or c) because you've had a look in Device Manager and seen it listed as such *and* it was working ?
I am right in saying that wi-fi was working, it's just the Intel Proset management tool wasn't installed/available ? Proset supports just 3 Intel chipsets, 2200, 2915 and 3945 - if you don't have any of those then that may be why you were getting the "adapter not found" error
Have you gone through the process I suggested (noting point 2),
From Device manager, remove the wireless adapter then re-boot the machine.
On re-start XP "Found New Hardware" wizard should start but cancel it.
Then go to the unzipped contents of the Toshiba package download and run the Setup routine from the "top" of that folder. That should install the Toshiba-provided driver and the Proset s/w
If you have just uninstalled the wireless driver and let XP do its thing, it would only have installed the Atheros driver if the wirelss card identified itself as Atheros (hardware has code built in so the computer's BIOS and then operating systems can figure out what the harware is and apply the appropriate drivers - this is how the Windows "Hardware wizard" works - it probes the device, reads the id code, identifies the correct driver, or calls it an unknown device because the piece of hardware is maybe newer than Windows) - you can manually "force" another driver to be used by hardware but almost always that piece of hardware just won't work with the "wrong" driver.
If you do in fact have an Atheros chipset-based card then you *will* need the Atheros driver and Proset won't work.
So I guess we need to step back and ask, exactly what wireless card do you actually have in your laptop?