Can't recognize modem

[waterlily]

I see that this topic is part of the intro to this site so it must not be a rare problem. But it is new to me. I have a USER with a Dell 400mh Win98SE system. I am trying to install a USRobotics 56K modem on a serial port. I believe it worked fine when I first installed it a few months ago. The user has not tried to use the modem since then but she wants to use it now. And now I can't get it to connect. The modem ctrl panel diagnostic finds nothing. I installed the USRobotics modem manager but it finds nothing also. This computer only has one serial port: com port 1.
Why wouldn't the computer be able to find it? It's basically a new computer and a new modem and the drivers are basically new. I have seen in other posts the recommendation to check the IRQ. I believe it is currently set to the default of 4. Could this be it?

[Susan]

You may need to have Windows recognize a new COM Port... do so within the Add New Hardware Icon in the Control Panel. Let Windows find the new hardware.

Once the system has rocognized the COM Port, the modem should be seen.

[Cadaver]

Com 1 and 3 share an interrupt of 4. Com 2 and 4 share 3. Is com 1 in use? (like a serial mouse) If yes, then you need to set the IRQ to 3. also, you never state if the modem is internal or external, PCI or ISA? More info is needed for a proper diagnosis.

Jay