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. However, that’s not really the case.
In fact, all other extensions such as .DOCX and .PPTX are all having the same problem, so the associated files won’t open if I tried to access through Microsoft Office XP or Office 2003. Luckily, Microsoft has an official support page related to this problem which comes as a great relief to Office users.
Microsoft Office compatibility Pack
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 (37 MB) will help you to open, edit, and save .xlsx files in Office 2000, Office XP, or even Office 2003.
Before installing Microsoft Office compatibility Pack, users that use Microsoft Office 2003 or Microsoft Office XP programs such as Word, PowerPoint and Excel please be sure to get all High-Priority updates installed on your PC.
How to install this download
1. Make sure to update your Windows with all high priority updates from Microsoft Update. This is compulsory for Microsoft Office 2003 and Microsoft Office XP users.
2. After you have installed the above-mentioned updates, download the Compatibility Pack into your PC.
3. Double click on FileFormatConverters.exe to initiate the installation.
4. Follow on-screen instructions to finish the installation.
After successfully installing the Compatibility Pack you can now open new file formats from Microsoft Office Excel, Word and PowerPoint 2007 in the previous version of Microsoft Office (i.e. Office XP, Microsoft Office 2000 and Office 2003).