To remove a password from a password protected Excel document, do the following:
- Change the file extension to .zip from .xlsx.
- Extract the whole content of zip file.
- Search for xml format of targeted sheet. It is in "xl\worksheets" directory (eg: sheet1.xml).
- Open the xml file of targeted sheet in a text editor (notepad++)
- Search for "sheetProtection" word in that xml file and remove it (remove the whole thing from <sheetProtection ... to />
- Save this edited xml file and re-add everything to the zip archive.
- Finally, change the extension from .zip to .xlsx.