When Windows starts a message appears saying ‘Cannot register with sm56 driver. Press OK to exit’. The problem only began to occur after installing Norton Antivirus 2005. The computer is running Windows XP.

This error message is related to the Motorola SoftModem driver installed on your machine, probably because your modem is based around the SoftModem architecture. This is quite a common problem, although I am unsure why the problem only began after installing Norton Antivirus 2005. You should try upgrading your modem drivers to the latest version. Go to www.motorola.com/softmodem/sm56_download.htm and download, then install the drivers for Windows XP.

Most people who experience this error are not able to use their modem, so judging by the ISP you are using (from your email address) and that you have not mentioned having internet problems, I assume that you are using broadband internet and don’t need the modem. In this case, if you are unable to solve the problem by installing the latest drivers you can try disabling the modem, which should stop Windows trying to load the drivers. Go to the ‘Start’ menu > ‘Control Panel’ and open the ‘System’ control panel. Click the ‘Hardware’ tab and the ‘Device Manager’ button. Expand ‘Modems’ and right-click on your modem, then select ‘Disable’. In the confirmation window click Yes. Now you should notice a red cross over the icon for the device and the message should not appear on startup.