Apparently this phone just needs a serial interface for data. Win7 should be able to recognize it as a serial port, and if it doesn't recognize it automatically there are ways to tweak the port settings manually.

"If no dedicated driver is available, it is recommend using the standard Windows 33,600 bps modem, with the port speed set to 115,200 bps." this is from the last line in this page http://www.inmarsat.com/Support/Fleet_33/Getting_started.aspx?language=EN&textonly=False#h

Let us know if this helps.