Excel

You export a CSV from a bank portal, a shop backend, a lab instrument, or a colleague’s Mac. You double-click it. The columns are right, the text is wrong: Müller shows as Müller, Café as Café, apostrophes turn into ’, and a column of Japanese or Greek names becomes rows of ????? or empty boxes. Nothing has been corrupted. Excel read every byte correctly and then decoded them as the wrong character set. That is a fixable mistake — but it has to be fixed in the right order, because one of the obvious moves destroys the data for good. ...

A workbook that will not open usually fails in one of three ways: Excel reports the file format is wrong, it offers to repair and then repairs nothing, or it opens to a blank or partially empty sheet. Each has a different cause and a different first move. Try these in order. The order matters — step 6 is destructive, and steps 1 to 5 are not. ...

You open a workbook and get: We found a problem with some content in ‘report.xlsx’. Do you want us to try to recover as much as we can? Click Yes, and Excel “recovers” the file — usually by deleting something. Click No, and nothing opens. Either way you do not learn what was wrong. This message is different from the generic “file is corrupt” dialog. It means the package is structurally valid and one part failed validation. That is a much better situation, and it is diagnosable. ...

‘report.xlsx’ is locked for editing by ‘another user’. The message is precise and almost always wrong about who. Excel does not track users — it tracks a lock file sitting next to the workbook. If that file is stale, the lock outlives the person who created it. ...