The speakers in most laptops are crap, so there isn't much you can do apart from adding external speakers. If the speakers are blown in your laptop you can replace them but otherwise there aren't many options since there isn't a market for upgraded laptop speakers.
You may also be able to tweak your sound settings for more volume and you could always look online to see if there are any drivers for your computer's audio that might address some sort of issue with low volume if it was problematic with that model.