Robertfr,
This is a dial-up software modem, right? You likely have no Vista drivers
for it, so now it doesn't work (likely cause).
If I understand this situation, try running the modem using WinXP SP-2
compatibility mode.
You should be able to find the option for doing this by right clicking your
dial-up icon and selecting Properties. In the window that opens, click on
the Compatibility tab. Select the proper mode there.
If that don't work, and you can't find Vista drivers (from the modem
manufacturer), then you have to purchase a replacement modem that is Vista
compatible. Also, try contacting the modem manufacturer for help and support
(by E-mail).
Another approach is to find the modem in Device Manager and try updating the
drivers from there (under Properties > Driver tab) for the modem. Device
manager should also display what the problem is for the modem. Just some
thoughts. Let us know what
happens.