Launch your open-source productivity suite and open the Presentation option, also known as Impress. Open the ODP file you wish to convert to a PPT.

How to change the default program a file opens with in Windows 7 When you open files that have a particular file extension, Windows will look at its configuration to determine what the default ...

Open the ODP file in Impress, the OpenOffice parallel to PowerPoint. LibreOffice, an alternative office suite, also uses the name Impress and supports ODP files.