Thanks, based on your idea, I made a bootable USB with the ISO file. As I go through setup, I get the installation point, and I get the error "Your computer started using Windows installation media..." . When I reboot, I'm back to 8.1.
Again, when I try the windows update, it shows the 10130 preview update, goes through the entire process, shows no errors, just installs, then reboots into 8.1. No idea why. Frankly, I'm worried it will do it when the final is released, whatever is going on. Any ideas?
FWIW, I installed an SSD drive, and cloned the OS to it. The factory HDD is in there, I haven't partitioned it yet. Could that be jacking it up somehow?