Set Oracle Home (install Oracle Home) for Toad 12.6
Here's what worked, although I don't know if it's a good answer or not.  I had someone who could log in as an admin on my pc do the Oracle client install.  In other words, if you're not a full admin on your machine, it may fail, and not tell you why.

I had admin rights, I could edit the registry and path, but there were still some missing rights.  Logging on as administrator and doing the install worked fine.