In order to fix the sound issue, go to Start, type dxdiag in the Search programs and files field and open the utility. Click the Sound tab, check your sound card model and download and install the latest drivers available from the developer web page.
If it doesn't help, go to Start > Control Panel > Hardware and Sound > Sound, right click anywhere in the Playback window and select Show Disabled Devices. After that, double-click on your device and select Enable from Device usage. Click Apply, OK, select again the device and click the Set Default button. If it still doesn't work, uninstall the software, run a registry cleaner and reinstall it.