you must install the sound driver. You also need to imstall the drivers of the mainboard (chip set driver, maybe also usb,lan) for really good working. At the moment, your system will work with the non optimal drivers from Microsoft.
You have probably got a cd with the laptop, maybe called drivers disk? This has all the drivers that you'll need. Or did you install Windows XP, even if Vista was previously installed?
Then you'll need new drivers for Win XP, you'll most likely find them on the laptop manufacturer's website. If not, give a hint what brand / model it is