Stop for physical warning signs
Power down if a hard drive clicks, grinds, repeatedly spins up, disappears, or makes the PC freeze whenever files are opened. Repeated restarts and scans can place more stress on a failing device.
Treat Windows warnings seriously
A critical storage warning, repeated file-system errors, or sudden read-only behaviour deserves a current backup and an assessment. Do not format the drive just because Windows offers to do so.
For accidental deletion
Stop saving or installing files on the affected drive. New writes can overwrite deleted data. Record which files are missing and what happened immediately beforehand.
Set realistic expectations
Recovery depends on the device, damage, encryption, and what has happened since the loss. No responsible assessment can guarantee recovery before the storage is examined.