When I try to connect to my ISP via dialup, I get the following error,

"Error 633: The modem (or other connecting device) is already in use or is not configured properly."

The only program I can detect that could possibly trying to use the modem is called "Modem On Hold" but I have turned it off. When using the troubleshooter I am prompted to check ports in Device Manager but interestingly the Ports listing is missing from Device Manager!

Any suggestion? (I am using XP Home SP2)

Many thanks.

http://www.modemsite.com/56k/duns633.asp

See if this helps.

What you need to do, is you need to check your irq ports, it sounds like you may have a conflict there... Has the modem worked before? If so, have you installed any other new devices? Like a sound card?