Does your system have a mixer control panel (double click on the Volume control)?
If so, the settings may be incorrectly configured, an input/output muted or the sliders turned down too far.
Or you may be using a virtual player with the sound setting turned down too low.
I presume as you have only had the Vaio for such a short time you have XP. Go to Control Panel and also check Sound and Audio Devices' Volume and Audio tabs' configuration.