1) Double check speakers are plugged in (usually to Green coloured audio line out port)
2) Test speakers with another device if necessary to confirm speakers work
3) Right click the speaker icon from the system tray (bottom right hand corner)
4) Click Playback Devices
5) When audio is playing in this window you will see a green equaliser bar showing sound is playing
6) Right click this audio device and click "Set as Default"
7) Close the application your getting sound from, re-open it and test again
8) If this still doesn't work then it's likely either something is broken, or you have missing drivers
To check for missing drivers, click start, right click my computer, click manage, click device manager and check the list for any warning symbols on any devices.