You can try to insert slides into a blank presentation
Step 1: Create a blank presentation
In PowerPoint 2007, click the Microsoft Office Button, and then click New. In PowerPoint 2010, click the File menu, and then click New. Click Blank Presentation, and then click Create. This process creates a blank title slide. You can delete this slide later after you re-create the presentation.
Step 2: Insert the damaged presentation as slides
On the Home tab, click the arrow next to New slides in the Slides group, and then click Reuse Slides. In the Reuse Slides task pane, click Browse. Click the damaged presentation, and then click Open. Right-click one of the slides in the Reuse Slides task pane, and then click Insert All. If this operation is successful, all the slides from the damaged presentation, except the slide master, are inserted into the new presentation. In PowerPoint 2007 click the Microsoft Office Button, and then click Save. In PowerPoint 2010 click the File menu, and then click Save. Type a new name for the presentation, and then click Save.
Step 3: Apply the damaged presentation as a template
If the presentation does not look the way that you expect after you try these steps, try to apply the damaged presentation as a template. To do this, follow these steps. Click the Microsoft Office Button, and then click Save as. Type a new name for the presentation, and then click Save. This will make a backup copy of the restored presentation, in case the damaged presentation damages this new presentation. On the Design tab, click More in the Themes group, and then click Browse for Themes. Click the damaged presentation, and then click Apply. The slide master of the damaged presentation replaces the new slide master.