Microsoft Excel contains encryption features to heighten security of your spreadsheets. Once enabled, the file cannot be viewed without entering the appropriate password. If you no longer require the encryption, the password can be easily removed.
Open the encrypted spreadsheet in Excel, which will require your password.
Click the circle in the upper-left side of the Excel window. This will appear just before "Home" on the menu and will have a Windows logo inside. In the drop-down menu, select "Prepare" and then "Encrypt Document."
Delete the password in the window entitled "Encrypt Document." Press "OK" to remove the password from your spreadsheet.