Ovladače pro Vistu dle mého neexistují a myslím, že ani nebudou. Nicméně můžeš zkusit řešení, které jsem nalezl na jiném diskuzním 4u :

USB ADSL Modems

* Webpower USB ADSL (based on GlobespanVirata chip) - works fine
with Zoom Modem USB ADSL drivers for XP (but you have to select the
right modem from the connection property because by default a wrong
NULL error modem is selected; check the modem properties using the
IE7's Connections tab -> Settings -> Properties). If the device is not
recognized after the software drivers installation, go to Devices
Manager and press refresh button so the drivers are installed.

* Zoom Modem USB ADSL (based on GlobespanVirata chip) - you can
install the old XP drivers but you have to select the right modem from
the connection property because by default a wrong NULL error modem is
selected (check the modem properties using the IE7's Connections tab ->
Settings -> Properties).