I found a Troubleshoot Guide for (my) Toshiba laptop but it should be generally applicable.
Some recommendations have already been suggested by other members.
No Sound
-Make sure you have latest bios version installed.
-Try to adjust your volume with the volume control on your case (if available) and in the "Volume Control" of Windows. ---Some notebooks have a key combination (FN-xx) instead of an external volume regulator to regulate the sound volume. In this case please check the user manual which key combination is needed for volume regulation.
-Make sure that sound was not accidentally muted or the soundcard was not disabled in the "Device manager" of the "System Properties". Try to re-enable/un-mute it by software or with the key combination "Fn-xx" if possible.
-Check in the sound properties, if the correct output device (e.g. speakers, headphones, digital/optical out, HDMI) was selected. In some cases you have to set the correct output device manually.
-Try to remove the soundcard from the "Device Manager" and reinstall it. Update the soundcard drivers and the software to the latest version. (Uninstall every sound related software and drivers before installing a newer version!).
-Try to connect some headphones to the headphone jack of the machine to check whether the system speakers are faulty or not.
-If the problem persists, reinstall your operating system, update all drivers and try to regain sound with "factory-preinstalled" settings.
*Check the FN key combination for your laptop.
Sound Troubleshooting
