Compaq Armada M300 Series Reference Manual page 84

Set the modem to ignore dial tones—If the modem
n
receives a dial tone it does not recognize, it will not dial
and will display a No Dial Tone error message. To set the
modem to ignore all dial tones before dialing:
1. Select Start à Settings à Control Panel à Modems.
2. Select your modem, then select Properties à Connections
tab, then clear the Wait for Dial Tone Before Dialing
check box.
6-8 Using an Internal Modem (available on select models)