Toshiba fan (Etch, Tecra 8100)
I think I've made some progress. Remember I'm running Etch, not Lenny, on an old Tecra 8100 (which AFAIK has a Toshiba BIOS).
After loading the required modules:
# modprobe toshiba
# modprobe toshiba_acpi
successfully, toshset changed its error message:
# toshset -q
toshset: this computer is not supported
I gave up using toshset for the time being.
Meanwhile, there's another program: FnFX. From the documentation:
FnFX enables owners of Toshiba laptops to change the LCD brightness,
control, the internal fan and use the special keys on their keyboard
(Fn-x combinations, hot-keys).
The packages are fnfxd (daemon) and fnfx-client, available in the main repo (in Etch).
My laptop is listed in the documentation (in /usr/share/doc/fnfxd/) as a 'verified Toshiba model'.
After installing them, I have been able to switch the fan on and off with Fn-3. The file /etc/fnfx/fnfxd.conf lists the keys and their functions.
Hope this helps Mirto and/or someone else with the same problem.