You no longer need third party tools to trim audio/video files to incorporate into your PowerPoint presentations. With PowerPoint 2010 you can now trim or clip out the unwanted portions of the clips.
To Trim an Audio Clip:
Click to select the audio clip you inserted
Under Audio Tools, Click the Playback Tab
Click Trim Audio
4. In the Trim Audio dialog box
5. Drag the green slider (starting point) to the right and the red slider to the left or until you’ve selected the segment that you want to use. You can also type the start and end time or nudge it frame by frame.
6. Click the Play button to test
7. Click Ok to trim the audio file.