Your computer thinks it should answer the phone. In and of itself, this
is not a Windows problem, as the computer is physically off when the phone
rings. Consult your computer manual, and look up the BIOS settings. Call the
vendor who sold it to you, and talk with their tech support people. There is
normally a BIOS setting that allows you to enable or disable this feature.
It has probably been enabled, and once you find the setting, you will be
able to disable it. As I dount that such a setting is enabled by default,
choosing the default BIOS settings will probably disable it if you cannot
find it.