|I would prefer guide below or another methods are proposed from different sources over Internet, but in case the guide from MS Corporation can't handle the problem|
https://www.openfiletool.com/pptxop... PPTX Open File Tool
1. Open PowerPoint 2007.
2. Click the Microsoft Office Button and click Open.
3. In the File name: box, enter the text in bold to display a list of the automatically saved files (if any).You can also copy and paste this text into the File name: box.
PowerPoint 2007: %temp%\ppt*.tmp
4. Click the Open button.
5. Click the name of the file that you want to recover, and then click Open.
Note : The automatically saved files may not be named in a descriptive way. Continue to open files until you find the one you are looking for.
6. After you find the file, click Save. Then save the file to your My Documents or other location.