How to Open .XLSX Spreadsheet Files Without Excel 2007

Files with extension xlsx is the default extension for spreadsheets written in Microsoft Office Excel 2007. I really thought the extension was made backward-compatible and you don't have to worry when you are about to open the files in previous version of Microsoft Excel like Microsoft Office Excel 2003. In fact, That's not really the in case.
One way to get around the problem is by converting the .xlsx spreadsheet to the traditional .xls format using the Microsoft Office compatibility Pack. The FileFormatConverters.exe (27.5 MB) will help you to open, edit, and save .xlsx files in Office 2000, Office XP, or even Office 2003.
To install this download:

1. Ensure your system is up to date by installing all High-Priority/Required updates on Microsoft Update (required for Microsoft Office XP and 2003 users).
2. After installing all High-Priority/Required updates with Microsoft Update, download the Compatibility Pack by clicking the Download button above and saving the file to your hard disk.
3. Double-click the FileFormatConverters.exe program file on your hard disk to start the setup program.
4. Follow the instructions on the screen to complete the installation.

Download Microsoft Office compatibility Pack