An 680 error in Windows (version doesn't matter, correct me if I'm wrong) means that there is no dial tone, check if your phone line is connected to the wall and to the port correctly... check if the phone jack you're using is working properly and etc....

Some more info for you:

There is no dial tone. Make sure your modem is connected to the phone line properly.
Possible Reason
The line is being used when you attempt to use it with your modem
Solutions
1. Make sure that they can hear a dial tone through the modem
2. Make sure your telephone cable is plugged into the line or telco socket of the modem, not the phone socket
3. Uncheck Wait for dial tone before dialing option at modem properties
From: http://www.inet.co.th/support/inetgold/faq.html

jag291