My old SSD I used for my OS was failing. It was some offshoot 128gb drive that I literally only used to house the OS (Win10 Pro). I installed the drive, formatted and made a partition for the OS on the new drive. I then made a bootable USB device, booted the PC and installed Windows 10 to the partition with no issues. I removed the USB, turned the PC on, and got the "Reboot and select proper Boot Device or Insert Boot Media in selected Boot device" error. So I booted from the USB again, the partition shows up and shows that of the 100gb I allocated only something like 78gb was free. So clearly it wrote. So I put the original drive back in and booted, it boots and asks me which OS I want to boot to and lists 2. It boots to the new drive if I select it from there, and it shows up in DiskPart. I checked the BIOS and the drive is selected as the 1 boot priority. I'm stumped. Thoughts?