My old computer SSD died, and a friend lent me an HD with a temporary install of Windows 10. The borrowed drive works perfectly, but it's a loaner. So I downloaded the Windows 10 formatting/installation tool and installed it on an 8 gig USB stick, then went to the BIOS and changed it so the USB booted first. I installed Windows 10 on a 120 gig partition on a new 1 TB SSD drive. I bought a serial number, and put it in, followed by all the startup mumbo-jumbo. Fresh new drive with Win10 installed on it, and everything looks perfect. I had the borrowed HD with Win10 on it, the new SSD with Win10 on it, and an HD with a copy of Vista on it, in that physical/plug order.
However, once I shut down, I unplugged the borrowed HD, went into BIOS and changed the first bootable to the new SSD. The first plug was empty, then the second had the new SSD, and the third had the old HD.
The next time I powered it on, Vista startup repair came on and tried disk repair to no avail. I double-checked I had set the BIOS settings correctly, and again, Vista startup repair. Tried using the advanced settings to check on whether the disk had other issues, then turned it off and replugged-in the borrowed HD and rebooted. Now it gave me the choice which Win10 HD I wanted to boot with, and it booted without major issue. I have done disk repair on the new drive, I have tried switching it so the new SSD is the first plug and the old HD is the second, and nothing seems to work -- if I don't have the borrowed disk in the lineup, the entire thing won't boot.
Where should I be looking next?