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Insert the slides into a blank presentation, and then apply the damaged presentation as a template to preserve the master. To do this, follow these steps:
1. On the File menu, click New.
This creates a blank Title slide. You can delete this slide later on after you re-create your presentation.
2. On the Insert menu, click Slides from files, and then click the Find Presentation tab.
3. Click Browse, select the damaged presentation, and then click Open.
4. Click Insert All.
If this is successful, this operation inserts all the slides from the damaged presentation, except the slide master, in the new presentation.
5. Save the presentation. If your presentation does not look the way that you expect, try to apply the damaged presentation as a template. To do this, follow these steps:
a. Make a backup copy of your presentation.
b. On the Format menu, click Slide Design.
c. On the Slide Design pane, click Browse.
d. Select the damaged presentation, and then click Apply.
The slide master of the damaged presentation replaces the new slide master.
Note If you start to experience unexpected behavior, the template may have corrupted the presentation. In this case, use the backup copy and re-create the master slide.