Here are key excerpts from my chat session with Vijay: I then took the drastic step of asking for assistance, using HP's Active Chat facility.
To start with, I had been unable to get the finger print reader working on my 64-bit version of Windows 7, despite numerous forum searches, downloads from the HP website and driver/software installation (Validity Sensor driver, plus either Verisoft Access Manager or Digital Persona). It was during an attempt to install the Verisoft fingerprint software that I realised that the OS was 32-bit, which then prompted a full reinstallation. The fingerprint scanner - a Validity Sensor VFS451 - was not available as a login method on the initial computer configuration.