Thanks for all the information and good suggestions.
I started out with Windows 7 32-bit on both my HTPC's. My goal was to move to Windows 10 with media center working with my Ceton network tuners installed on my server. I also had the secondary goals of moving to 64-bit to accommodate some light gaming, making use of a Metro-style UI and "tablet mode" with custom tiles for streaming and music services.
I have discovered that:
1. Media center on windows 10 runs fine.. as long as you don't try to do anything useful with it.
2. Tuners don't work under media center. Media center doesn't "discover" the tuners during the live-tv setup.
3. It's not possible to make custom tiles for Windows 10. You can go to the play store and look for them, but most of the time they're not there.
So since, at an absolute minimum, I have to have Live TV working in Media Center, I gave up on Windows 10. I decided to try Windows 8.1. I figured my fortunes would be better since, technically, Ceton supports Windows 8.1 and media center is available on that version of Windows.
I further discovered that:
1. Media Center is NOT available on Windows 8.1 anymore. I had to use the hacked version of it I had for Windows 10.
2. The Ceton drivers do not support network tuners, but I managed to get them installed anyway.
3. Playready refused to install and I grew tired of trying to make things work.
4. The Metro UI for 8.1 is.. not ideal for Media Center use.
So, as of right now, I have further downgraded to a 64-bit windows 7 install. Media Center is working, Tuners are working and I'm (mostly) back where I started. My only accomplishments thus far have been a successful move to a 64-bit OS.