How to recover an image after a crash
Paint by Zaweba writes changed documents to a Recovery folder every few minutes and offers to reopen them after a crash or power cut.

After a crash, Paint by Zaweba's auto-recovery is what brings your image back. Every few minutes, on an interval you can set, it writes any changed documents to a Recovery folder, and the next time it starts after a crash it offers to reopen them. Accept, check the recovered file, and save it properly straight away.
Crashes are rarer than they used to be, but power cuts, Windows updates that restart the computer and drivers that fall over still happen. Recovery is there so an afternoon's work doesn't disappear with them.
What happens after a crash
Start Paint again. If documents were waiting in the Recovery folder, it offers to reopen them. Say yes. Each comes back as it was at the last recovery save, so you may lose the last few minutes, but not the whole session.
Look the file over before carrying on. Then choose Save As and save it as a .ptx with a new name, so you have a proper copy. Don't rely on the recovery copy as your working file.
Setting how often it saves
The interval is N minutes, a setting you choose. A shorter interval means less work lost if something goes wrong. For heavy files on a slow drive, a few minutes is a fair balance; for quick sketches, a minute is fine.
Reopening your last session
Separately from crash recovery, Paint can reopen the documents that were open when you last closed it. Turn that on and every session picks up where you left off. File > Reopen Last Session does the same on demand. The Recent Documents panel shows thumbnails of files you've worked on recently, which is often quicker than hunting through folders.
Good habits that save you
Save often. Ctrl+S is still the best protection there is, and auto-recovery is a backup to that, not a replacement.
Save in .ptx while you work. It keeps every layer, mask and adjustment editable. A flattened JPEG saved mid-session loses all that.
Use version numbers for big jobs. Save As a new name at each stage, such as portrait-01 and portrait-02, so a damaged or spoiled file isn't your only copy. Snapshots in the History panel, saved inside the .ptx, are another way to keep return points.
Keep the working folder on a drive that's backed up. Recovery covers crashes; a backup covers a failed drive or a deleted folder.
When recovery can't help
If you closed a document and chose not to save, it's gone, because you asked for that. If the computer crashed before the first recovery save of a new document, there may be nothing to recover. And if you saved over a good file with a bad edit, recovery won't bring the old version back; turning on saved history in Preferences > History, so undo survives closing a file, is the safety net for that.
Paint by Zaweba is a free, offline image editor for Windows. Recovery files are written to your own computer and nothing is sent anywhere.