This short tutorial assumes that you have Windows Media Encoder installed. This software can be downloaded for free from Microsoft (if you have a genuine copy of Windows). This is not the only available software. In fact, you can use any software, which can export to a movie/video file.
download Windows media encoder

Start Windows media encoder. It is advisable that you have your presentation software running with the presentation in full screen mode. You can switch between windows using the Alt-Tab keys.

select the Capture Screen session

Choose the region you want to capture - for MS PowerPoint presentation it is best to use full screen. Make sure you select the Capture audio from the default audio device in order to record the voice-over.

Name the video, that is provide the name you want it saved under.

Select the quality of the output. Since we are targeting Internet distribution, don't select High - Medium should be sufficient.

Fill in the appropriate metadata

Finish with the wizard.