dial-up modem and the present

I have gifted my dad a new pc with win 7 home premium. He lives on the countryside and on his old machine, he was running a 3com U.S robotics 56K message modem (serial).
The new mainboard (MSI G41M-P25) has no serial connector, so I brought a serial-usb adapter hoping that the modem would just be recognized, but no. I have already sifted through a few sites looking for drivers (the adapter seems to be the problem, robotics do have a win7 driver for that modem on their site which I installed).

If I don't succeed in getting that modem to work on that machine (any experiences with a similar config btw?), I am guessing the options are: a modem with a usb connection or even an internal modem card (1x PCIe x16, 1x PCIe x1, 1x PCI slots inside) OR a internal card that offers a serial connector so the old modem can be used.

Am I too simplistic/optimistic, and are there any pitfalls in my scenarios, specifically with respect to that modem hooking up to the internet under win7?

thanks,
delgado

Thank you. I'm confused: the modem connects the pc to a telephone landline, how would a whip antenna have any bearing on the quality of data reception?

I installed the 32bit version, and I assume that would make things easier, since the driver problem/shortage seems to be on the 64bit side, right?

anything else I need to watch out for re specs (thinking of the 56kb/V.90 or 92 numbers)

thanks