I found a pretty easy way of disabling the password protection in the new Excel Worksheet files (XLSX) used by Excel 2007 and 2010. Just follow these simple steps:
- Change the file extension from .XLSX to .ZIP
- Extract the file to a folder with your favorite unzipper (7-Zip is what I used)
- Go to the xlworksheet sub-folder that you just extracted
- There should be one or more files named like: sheet1.xml (sheet2.xml, etc). Inside of one of those files is an XML tag: <sheetProtection password=… />. Delete that entire XML tag.
- Re-zip the files back up
- Rename from .ZIP to .XLSX
UPDATE: This method only applies to password protected workbooks. If the file is secured with the “Encrypt with Password” feature, it will not work.