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Below are the steps to unlock any Excel sheet if you forgot the password
If your file is .xls then save it as .xlsx if it doesn't have any macros or .xlsm if it has macros. Let us assume your file name is ProtectedWorkbook.xlsx
1. Rename your file by adding .zip to its extension. In our case we will rename it to be ProtectedWorkbook.xlsx.zip
2. Now open the zip file with windows or any program.
3. Browse to the path xl > worksheets folder
4. You will find an xml file for each sheet. Extract the protected sheet xml file to your local drive. In our case, its name is sheet1.xml
5. Right click the extracted sheet1.xml file and select edit to open it in notepad or any other editing software.
6. Find an delete the text starting by <sheetProtection and till the closing >. In other words, from the <sheetProtection till the first > occurrence.
7. Save and close the sheet1.xml file
8. Return the edited sheet1.xml file to overwrite the original one in the zip folder.
9. Close the zip file
10. Rename the file ProtectedWorkbook.xlsx.zip by removing the .zip extension
Your sheet is now unprotected.