No sound on video when i play it back on my PC

1. Install a multimedia player which can play the camera videos (.mp4, .mpeg, .dat files) like VLC Player, Real Player, KMP Player, etc.

3. You can also play these videos on the media player which came with the software bundle (CD) of your Sony Cyber Shot camera.

tell me if it helps...tc! :)

For no sound issue on your PC, maybe you can check on these articles as there might some different reasons for the issue:
Windows Media Player Plays MTS Files with No Sound
Why No Sound on QuickTime Video
How to solve MP4 having no sound