Actually, if the modem and the driver disk both came from the OEM then I would say that there is a very good chance that they are there.
Hey, just a suggestion from a long ago simple problem. Is it turned on? as we would say in the theater or in TV. The internal network card on our main tower for years didn't work although until I needed it for high speed I wasn't all that concerned. Well it was as simple as that the stupid thing wasn't turned on inside the BIOS section so the machine never knew it had one to associate the drivers it did have. So once this nice guy and I from Gateway went into BIOS on a boot sequence, all was golden. I've been using the same card for years now, no problems. As an old tech I felt so embarressed, although the OEM never properly activated this part of the system that they built for me.
Sometimes it really is the simplest of things.