Every time there is a phone call the computer turns itself on. I have heard it is possible the computer is infected with a virus, but several scans with Norton Antivirus do not show any viruses.

The key to this problem is that the computer turns on each time you have a phone call. It’s likely that your computer supports an advanced power management feature called ‘Wake-on-Ring’. This causes the computer to start each time the modem detects a phone call on the connected phone line. To stop this behaviour, you will need to enter your computer BIOS setup and disable this function. Restart the computer and during the power-on self test you should see a message like ‘Press DEL to enter setup’. When you see this message, press the nominated key (in this case, DEL) and the BIOS setup should load. Enter the Advanced Power Management (or alike) section/page of the BIOS setup, and look for a setting like ‘Wake-on-Ring’, ‘Wake-on-Modem’, or like which is enabled. Once you find this setting, change it’s status to disabled. Be very careful when changing settings in the BIOS, as accidentally changing settings could render your computer unbootable. If you are unsure of anything, always err on the side of caution and seek additional advice. Assuming you are able to successfully change the necessary setting, exit the BIOS setup and save the changes. The computer should restart and now should no longer automatically start when your phone line rings.