Lincoln,
I submitted the driver request a few years ago, and again today. I did not get a response. I am willing to share the cost of the development of a driver for this equipment. I took the driver for the newer HP35670 and started modifying it for use with the older HP35665. The driver modification is pretty complex because the newer analyzer has many new features not available in the older model so It has not been moving very fast. My whole project (using a DSA) has been on hold unitl I get a working driver for a HP35665, or I buy a new spectrum analyzer.
I decided that it would simplify the project by determining the exact measrurements I want to take with the HP35667. This reduces the project by not expecting said driver to fullfill every measurement capability of the HP35667.
Best Regards
John Burwell
Email me directly if you want to work on this project jointly in a web ex or other on line colaberation environment, sharing code and steps can ease the pain if this driver creation.