You might have spent days, weeks, months, even years working on some important Microsoft Office document. But it doesn’t make any difference. Just a few crucial corrupted bytes is enough to ensure that Office won’t be able to open it, and it’ll appear that everything you’ve done has been lost.

Don’t worry, though – there may still be hope. We set up a test to show how this might happen, and what you can do about it, and it turns out that just a few seconds with an obscure free Microsoft tool could be enough to recover your file.

Our trial started by selecting a readable .DOC file. Yes, .DOC; unfortunately the Microsoft program doesn’t work with the OOXML formats, .DOCX and so on. But there are still plenty of .DOC, XLS and PPT files around, and of course older files are more likely to have suffered corruption, so being able to restore their contents may still be useful.

Next, we launched the hex editor HxD, opened our test file and zeroed 12 bytes. Not just any bytes, either: we wiped the beginning of the document FAT, a crucial area that tells Word where to look for key file structures.

We saved the results, then tried opening our new file in Word 2010. And sure enough, we were told that “Word experienced an error” when trying to load the file. The error message recommended that we use Word’s “Open and Repair” option, but that didn’t work either.

If this were a real life situation then panic would be setting in around about now, but fortunately we had another option to hand, a little-known Microsoft tool called OffVis.

We downloaded a copy, unzipped it and launched the program (no installation is required). Clicking File > Open Data File allowed us to open the program, then we chose the Word parser from the Parser list and clicked Parse. Even OffVis complained that “an exception was thrown”; this wasn’t looking good.

But there was something else to try. Click Tools > Repair and Defragment in OffVis and the program will attempt to fix any problems. The interface is feeble – there’s no dialog box, no way to tell OffVis is even doing anything at all – but hey, it’s not like we had anything else to do. So we waited for a few seconds, then clicked File > Save Data File As, and saved the file with a new name.

Finally, we switched back to Explorer, double-clicked the new file, and… It opened. And all the contents were there. OffVis had fixed what the Office “Open and Repair” function couldn’t, successfully bringing our data back from the dead.

Now it’s important to be cautious here. Just because OffVis solved this problem, there’s no guarantee that it’ll fix any others. It’s not optimised for data recovery, and in some situations might even make a document worse (so always work on a backup copy). Still, if you’ve an old Office document that you can’t read in any other way, then OffVis just might be able to recover it for you.