How it works
A bootloader participates in loading the operating system after the platform’s initial startup stages. Boot configuration, storage access and security checks must agree. A startup error can occur before, during or after this stage, so “will not boot” is not a complete diagnosis.
A practical example
A computer that shows a firmware screen but no operating system may have a missing boot entry, inaccessible storage or damaged boot files. A machine that reaches the sign-in screen has already passed a different part of the sequence.
What to check
Record the exact message and the point reached. Check whether the intended drive is detected and whether a recent hardware or firmware change preceded the issue. Prepare recovery keys and backups before repair attempts that modify startup configuration.
Limits and safe next steps
Do not format a drive or delete partitions merely because booting fails. Avoid copying repair commands from a different platform configuration. Boot-mode and security changes can affect encrypted drives; follow the documented procedure for the actual operating system and hardware.