You can try following tricks:
1)Check the sound icon on system tray, open it and see no volume controler is muted. if so then unmute this.
2) If icon does not exist, then check for drivers update, Desktop>my computer>properties>hardware>device manager>check the sounds are installed.
3) if no sound is installed then installed sound driver from your backup or get it from CD shop or download it from internet with brand name.
if you want more information then try this one.