If you can’t hear any sound using Windows 7, the chances are, if everything driver wise is installed correctly, your audio playback device is configured to ‘headphones’ instead of ‘speakers’. You can check this by right-clicking the sound icon (bottom right of the Taskbar) and choosing ‘Open Volume Mixer’. Now play some audio (just click a video on youtube.com). If the green bars jump up and down everything is configured correctly, you just need to change the default playback device. Right click the sound icon again and choose ‘Playback devices’ from the resultant menu. You’ll then see this window:
Now just click on the speakers and choose ‘Set Default’ and then OK.