|"Dell Studio 15 laptop"|
That's not enough information. There are several Dell Studio 15 laptop models - 15xx.
Look for the label that's on the outside of the case - it probably has 15xx on it.
If it doesn't quote the Service tag number.
See Response 6 in this
" Make sure you don't have volumes set too low or muted, for things you want to hear or use.... "
If you have used the headphones jack a lot....
The headphones jack on laptops and netbooks has a mechanical switch inside of it. It's supposed to disable the sound from going to the speakers built into the laptop whenever you plug a plug (on a cord) into the headphones jack.
If you have plugged into the headphones jack a lot, it's common for that mechanical switch to malfunction. You could try plugging a plug into the headphones jack, wiggling it, then pulling it out, that may get one or both speakers working, but the only real solution is to replace the headphones jack - that's an item frequently replaced by laptop repair places.
OR - you could make do by plugging amplified speakers into the headphones jack.
However, if the right sounds "drivers" were installed the right way, and if the onboard sound is enabled in the bios (there is probably no setting for that in a laptop's bios), usually you DO have sound when you plug amplified speakers into the headphones jack. There are two jacks - one for headphones and one for a microphone - are you sure you're plugging into the right jack ?
The other usual reasons for the sound not working are the wrong sound "drivers" were installed, or the right sound "drivers" were installed the wrong way.
See response 3 in this:
We need your Dell Studio 15xx model number in order to point you to where the correct sounds drivers are on the Dell web site.