How to Encrypt an Excel 2007 File
Microsoft Office Excel 2007 is a powerful spreadsheet program that many businesses and individuals use to keep track of sensitive financial data. Microsoft offers users a convenient way to increase the security of that data by including an integrated encryption capability. This allows you to establish a password. Once you close the document, it will be extremely difficult to open it without the correct password. Though the encryption level is not as great as that offered by specific security programs, it is sufficient for most data.
Open the Excel workbook you want to encrypt.
Click the "Microsoft Office" button in the top-left corner of the screen.
Place your mouse cursor over the "Prepare" entry on the left side of the menu to bring up its options. Click "Encrypt Document" on the right side of the menu. A password pop-up window will open.
Enter a password for the document. Make sure you can remember it since you will not be able to recover the spreadsheet if you forget it.
Click "OK," re-enter the password and click "OK" to close the window.