The problem is most likely that this is a so-called softmodem. In "traditional" modems, the modulation and demodulation (the signal processing that the name derives from) was mostly done in hardware. The interface to the computer was standardized (serial connection with Hayes command set), so they worked without special drivers. However, computers can easily do that in software, so newer modems often off-load this task to the main computer to perform in software, hence "softmodems".
The problem with this approach is that these modems require special drivers for the computer, to do the software part. Traditionally, these drivers were only available for MS Windows, meaning the modems didn't work under Linux, hence they were sometimes called windodems.
Ironically, modern versions of Windows do not support these devices either, as the old Windows drivers no longer work.
To make a long story short - the device will not work under Windows 7 64 bit, unless you find drivers, or write them yourself.
You will need to find another modem. Either one with Windows 7 drivers, or a traditional serial modem (however, this will need a serial port, which most modern coputers lack).