HP PC wouldn’t start Windows

What the user needed

The user couldn’t get past startup on their HP PC. It displayed “Boot Device Not Found (3F0)” and a Secure Boot violation reporting an invalid signature. The user had backed up some data and asked me to restore access while protecting the remaining files and keeping repair costs down.

What I checked

I considered storage detection or failure, the firmware boot configuration and a bootloader problem. The invalid signature gave me a reason to focus first on the firmware’s verification step.

I reviewed the HP BIOS/UEFI settings and chose to test one change to see whether the existing Windows installation would start with Secure Boot temporarily disabled.

What I did

I disabled Secure Boot as a temporary recovery workaround. Windows 11 loaded, the user’s existing files were accessible, and I confirmed Windows would boot on a second restart.

I ran the built-in HP Hardware Diagnostics Fast Test. All components included in the test passed. An intermittent storage issue remained possible, so recurring boot errors would warrant further storage checks.

Outcome for the user

The user regained access to their existing Windows installation and files without reinstalling Windows, changing partitions or replacing hardware. No data loss was observed during the repair.

The user planned to back up the remaining important files. Completion of that backup was unverified.

Lessons and follow-up

A repeatable boot after one firmware change pointed to Secure Boot verification. The cause of the invalid signature remained unknown, and Secure Boot was still disabled at handover, leaving the PC without that layer of startup protection.

The follow-up would be to confirm the backup and access to any drive-encryption recovery key, then review Windows and firmware update history, trusted keys and bootloader compatibility. Once the underlying issue is corrected, re-enable Secure Boot and verify that Windows starts reliably.