Restart your system and choose the correct boot drive.
Restart your system and choose the correct boot drive.
Hello! Thank you for sharing your experience. I had a 250GB SSD and upgraded to a new 1TB SSD. After installing Windows 10 via the bootable USB, I copied files from the old drive (C drive now 1TB, D drive 250GB). When both drives are connected, I can select which one to boot from—Windows is on the 250GB drive and another on the 1TB. Everything works fine until I unplug the 250GB drive and try booting from the 1TB. It shows up as "Reboot and Select proper Boot device." After reinserting the 250GB drive, the OS selection screen appears again. It seems the system thinks the OS is on the 250GB drive but not the 1TB one. I considered checking if the EFI partition was missing on the 1TB drive using DiskPart, but that didn’t help. I also tried different boot orders and even set the 1TB drive as priority, but the issue persists. I attempted to use a bootable USB for Startup Repair, but it reported no action. I’m not keen on wiping the 1TB drive again. Any suggestions would be greatly appreciated!
Windows refuses to install multiple bootloaders when it finds one already on another storage device. Ensure only a single drive is connected during installation to prevent unexpected changes. Disconnect all drives and set up a fresh EFI partition on the 1TB SSD via DiskPart to resolve this problem.