If your modem was supplied when your PC had Windows XP on it, and now you have updated or bought new PC with Windows Vista on it, your modem may work or you may get away with just updating the drivers, if not get back to Tiscali and they will supply a new modem.
The introduction of Windows Vista has caused some problems throughout the industry. These are due due to incompatibility issues with other software. If you are upgrading to Vista there are scenarios where you may experience problems, such as being unable to connect to the Internet. This is due to incompatibility issues with your existing modem software and Vista.