Hi @DrDinosaur,
I understand that you are having some troubles with the fingerprint reader on your system, after installing the Windows 10 tech preview.
You may want to try updating to the current build which is 10162. Each update tends to have a series of fixes and new features, ( and sometimes a few more issues). Currently the only drivers for Windows 10 tech preview, are a part of the operating system.
Also please read the following post Welcome to the HP Windows® 10 Technical Preview discussion board.
by @Bill_F. It includes general information about the Tech Preview as well as links to the various Microsoft pages for preview.
Also if you wish to get the free upgrade to the release version of Windows 10, when it comes out, you will probably want to go back to your original factory operating system, to qualify for it.
I hope this helps.
Malygris1 I work on behalf of HPPlease click Accept as Solution if you feel my post solved your issue, it will help others find the solution.Click Kudos Thumbs Up on the right to say “Thanks” for helping!