How can I view a PowerPoint slideshow in windowed mode (ie, not full screen)?

This slideshow is only opening in full screen mode. I can't find any context menu options that will switch it to windowed mode.

Update: I am opening this .pptx file as an attachment from within a Word doc. Opening it that way seems to force to full screen. However, when I right-click the attachment and select Edit, it opens in actual edit mode within PowerPoint itself. Also, when I save the attachment and open it directly from the drive, it also opens in edit mode. This will suffice for now, but it would be nice to be able to switch a full screen presentation to windowed.

In the Ribbon, on the Slide Show tab, there's a button called Set Up Slide Show.

In there is an option called Browsed by an individual (window).

For Office 2016 (OS X), it's similar to the answer posted previously. You can go to "Slide Show" tab -> "Set Up Slide Show" -> on the popup, under the "Show type", choose "Browsed by an individual (window)" -> "OK".

Then "Play from Current Slide" will play the slide in windowed mode.