Hi,
Do you mean: "8720C Microwave Network Analyzer"?
It looks like you have to use the driver for the HP8753 (apparently the same)
If so, follow this link for the drivers:
http://zone.ni.com/idnet97.nsf/9b2b33e1993d877786256436006ec498/99fd4a9bfc561ba7862568ab005fbb48?OpenDocument
The better option is LabView. Well... That's really a matter of personal preference ;o)
-JLV-