If you are looking for an internal computer modem that will handle Caller ID, do not bother with the US Robotics 5670. They have very misleading info on their datasheet, and virtually no help to speak of on this issue in their support pages. However I found on a message board a person with my similar problem.
He was able to get an “OK” response to the AT+VCID=1 string in Hyperterminal, but still got no data when an incoming call occurred. Turns out, USR only implemented Caller ID on this modem when the user is connected to the internet through the modem. It doesn’t do Caller ID when the modem is idle. What a crock! Back to the drawing board.