After a blue screen, forced shutdown, or power cut, a file keeps its normal size but won't open — and Notepad/Notepad++ shows it's full of NUL characters (zeros) or blank squares instead of content

What's actually wrong

When Windows crashes while a file is being written, NTFS security design can leave the file's blocks zeroed out: the size looks right, but the bytes inside are all 00. If the ENTIRE file is null bytes, the original data is genuinely not in that file anymore — no tool can conjure it back, and you should hunt for auto-saves and shadow copies instead. But crashes often zero only part of a file, or the original survives in Office's own recovery locations, so check what's actually inside before giving up.

Free fixes — try these first

1. Let Office recover it. Reopen Word/Excel/PowerPoint — the Document Recovery pane appears after a crash. Also try File → Info → Manage Document/Workbook → Recover Unsaved Documents.
2. Hunt the AutoRecover and temp folders. Look in %appdata%\Microsoft\Word (and \Excel, \PowerPoint) for .asd files, and in %temp% for recent .tmp/.wbk files sorted by date — open candidates by renaming a copy to the right extension.
3. Windows Previous Versions / File History. Right-click the file (or its folder) → Properties → Previous Versions and restore a pre-crash copy.
4. Cloud version history. If the file lives in OneDrive/Dropbox/Google Drive, restore the last good version from the website's version history.
5. Check what's actually inside. Open the file in Notepad++ : if you see readable fragments mixed between NUL runs, partial recovery is realistic; if it's 100% NUL from start to end, the data is gone from this file — focus on the recovery locations above.

If the free fixes fail

When the file is only partially zeroed, our analyzer scans for surviving document fragments and quantifies exactly what's recoverable — and if the answer is 0%, the free diagnosis says so honestly instead of selling you a repair that can't work.