Microsoft Office 2010 has the ability to export the presentation as a video. Unfortunately, I discovered that the built-in conversion process degrades the audio significantly. In my specific case, the narration became tinny to the point of being unusable. That happened even when set at HD quality (no audio-specific settings were apparent), so I began looking at alternatives.
I have had luck with other Moyea solutions, so I was pleased to stumble across Moyea PPT to Video Converter. It took minimal detective work to determine that it was the same software as Leawo PowerPoint to Video Pro, which sells for $5 less. Regardless, I decided to start with the free trial. The comparison page links directly to a downloadable installer. WIth the quality set to high, the results are much better than with Office 2010 native conversion.
The trial version adds an intrusive watermark to the final video file. However, it adds the watermark during the final step. The initial raw mpg file that is stored in the Temp folder does not have the watermark. You should purchase the full version if you intend to use their product or its output, but you can access the uncompressed .mpg file in the Temp folder during the "Create output video file" step. During that step, that raw mpg file can be copied to another location. Given that any conversion results in some loss of quality, accessing that initial video file may always be the best option if you plan to submit the video to some other standardized process prior to distribution.
If you are not satisfied with the native conversion, and the software above does not fulfill your needs, then consider this list of free converters.