If you have an old Alcatel Speedtouch usb modem and are having the same problem as i had when installing Windows vista try downloading the driver from the link below.
http://www.speedtouch.co.uk/downloads/330/301/st330_3012_windows.zip
Before installing it make sure you unistall al other versions and drivers and restart.
Then Simply unzip the file and run the install file and all should be ok after that.