flash-память
Foolishly made format S: /FS:FAT32, where S is the volume labeled system, when it was loaded from a flash drive with Windows. Now boot devices are just a flash drive
I did the removal of ubuntu according to the guide, made the release of the partition, and then I had to boot from a flash dr ... continue launching Windows, but I did not have such a button. I rebooted and now only the flash drive is in the boot manager.