Optiplex 760 not finding modem

I have an Optiplex 760, dual core Pentium E5300 processor, 4GB of memory,  running Windows 7. It did not come with a dial up modem, but I need one to be able to fax. I bought a DELL 330 CONEXANT RD01-D855-005 INTERNAL MODEM CARD and installed it. The computer cannot find it. I tried downloading the driver and installing it, and it says, This item is not installed, cannot install drivers. I have uninstalled it and reinstalled it, tried everything I know, and no modem. Any help would be more than appreciated, thank you!!