Modem problems

I am trying to get a modem and dial up networking to work under XPeSp1
and am having some major problems. I have tried two different modems,
one external and one internal PCI modem.

If I go to the modem control panel and run the diagnostics for the
modems then I get back that data that I expect so at the most basic
level the modem driver have been installed.

If I try to connect using HyperTerminal then on the connection dialog
I see "Connecting..." for a second or so before it goes to
"Disconnected". If I try create a dial up network connection to an
ISP then I get an error 633 - "The modem is in use or is not
configured correctly".

I guess that I must be missing a component or two but I can't work out
what as I have pretty much anything that looks like it is related to
Modems or dial up networking included in the image.

Any one got any thoughts?

Thanks.

Andy.