If files are being deleted by mistake on a shared PC, office computer, USB drive, or project folder, start with free Windows options. They can reduce risk, but they do not always stop another user from deleting, renaming, moving, or overwriting important files. File Lock Pro is a better fit when you need repeatable selected-file protection.
The Windows read-only attribute can reduce accidental edits, but it is easy to remove. It is a light warning, not strong deletion protection.
NTFS permissions can deny delete or write access when users have separate Windows accounts. This is useful on managed PCs, but can be confusing on shared home or small-office computers.
Backups do not prevent deletion, but they reduce damage after a mistake. Use them for folders where recovery matters, especially project files, invoices, photos, and reports.
A ZIP or 7z archive can help preserve completed files, especially if you also store a copy elsewhere. It is less useful when the files are opened and edited every day.
Moving final files into a separate archive folder can reduce casual cleanup mistakes. It still needs access control if other users can delete the archive too.