See if you can find a driver here : Westell - Technical Support
If you can only find a xp or vista driver and it wont install normally you may need to install it in compatibilty mode, or thru device manager to resolve the OS mismatch - go here for details :
You cannot install a device driver by using its installation program in Windows Vista
To install a driver OR program in compatibility mode - right click the setup.exe file - click properties - click compatibility - check run in compatibility with vista/xp etc - check run as administrator - leave the rest blank. Start setup.exe and install.