Docx, xlsx, pptx files are formats used by higher versions of Office than Office 2003. Many users struggle to open these files in Office 2003. However, with the methods below, you can easily open docx, xlsx, pptx files in Office 2003.
This article provides guidance on three methods to open files: using the Microsoft Office Compatibility Pack File Formats upgrade, utilizing an online website, and leveraging Gmail.
Method 1: Use the Microsoft Office Compatibility Pack File Formats upgrade.
Download the Microsoft upgrade package from: http://www.microsoft.com/en-us/download/details.aspx?displaylang=en&id=3

This upgrade package enables Office 2003 versions to read formats from Office 2007, 2010 (.docx, .pptx, .xlsx).
After downloading the upgrade package, install it into your system. Then, you can open, edit, and save documents with formats (.docx, .pptx, .xlsx) in Office 2003.
Method 2: Use an online conversion website to convert formats .docx, .pptx, .xlsx to .doc, .ppt, .xls for compatibility with Office 2003.
Visit the website http://www.freefileconvert.com/
Under Convert File.
1. Input File: Click on Choose File to select a file with format (.docx, .pptx, or .xlsx).

2. Output Format: Choose the corresponding output format (.doc, .ppt, .xls).


After sending the emails, navigate to your Sent folder, and in the attached file, select Edit with Google Docs as shown below:

Once the window pops up, you can view the files (.docx, .pptx, .xlsx), highlight and copy all content into the corresponding Office 2003 file.
Above are three methods to open higher version Office files using Office 2003. There might be more approaches, but these three are the simplest and most practical. Choose the one that suits you best. Best of luck!