How can I get the sound louder on my Toshiba Satellite laptop?

I just bought a Toshiba Satellite laptop and I use it to watch DVDs. But the sound is so low on it I have to wear headphones, but then no one else can hear. Is there a way to get the sound louder? I have tried playing it on all the different DVD programs on the computer: Toshiba DVD Player, Windows Player, Windows Media Center and none of them give enough sound.

Other things like YouTube videos are more than loud, CD's, Limewire downloaded music and things like that, but just not DVDs.

Any suggestions???

TIA!