Did you save your PowerPoint presentation using the Save AS... option and save as an older format ie. PowerPoint 2003? Or did you simply choose Save (CTRL+S) from the PowerPoint main menu to save your presentation?

Since PowerPoint 2002, you have the ability to have as many Slide Masters as you need, so you can create presentations with slides that have different looks. and features.

To create or add a new slide master in your PowerPoint presentation.

Choose: View > Master > Slide Master command to switch to Slide Master View. Or click the Insert New Slide Master button.

A new Slide Master appears.

With the Slide Master Open you can now make any changes that you wish for example if instead of Click here to add title you would rather have a static text. Simply delete the Text object placeholder.

Now select the Text box tool and draw a text box on the slide where you want your slide title to be. Type in the text that you want all slides beneath this slide master to have.

Format the text box, (color set to none, line set to 0, etc) to remove the white background and bounding box.

Format the text in the text box the way you wish. Now close the Slide Master view.

Each time you now insert a new slide using this Slide Master it will have the text in the postion, style, and format that you assigned to it in the Slide Master.

As far as I know, you cannot change the Click here to add subtitle text in any version of PowerPoint other than PowerPoint 2007 and PowerPoint 2010 but maybe I am misinformed and if so some of our community members can correct me?