The next step is to click on the Office button, choose Prepare, and then pick Inspect Document. This will bring up the Document Inspector window as shown in the second screenshot above. Check the box in front of each type of content that you want to inspect. If you’re concerned about people accessing hidden personal data, make sure to check the box in front of Document Properties and Personal Information. Click Inspect to continue.

click to enlarge
After searching the content, the
Document Inspector will return with at list of items found and give you the option to
Remove each of these items, one by one.
Note the warning that removing some information cannot be undone. This is why it is best to be working with a copy of the original presentation.
If you haven’t created a copy of your PowerPoint presentation yet, you can click Close and no changes will be made. If you’re ready to go ahead and make the changes, click Remove All. Afterwards, to double check that everything was successfully removed, click Reinspect and repeat the process.
When you’re satisfied that all of the information has been removed, save the file again. Now you can share your presentation without worrying about any lingering hidden personal data.
Additional Resources: For more tips, be sure to take a look at the other Microsoft PowerPoint hints and tricks available here on Bright Hub's Windows Channel. New and updated material is being added on a regular basis, so bookmark the site and check back often.