|If you have NOT loaded Windows from scratch since the speakers last worked, the headphones jack on laptops has a tiny mechanical electrical switch inside of it that disables the built in speakers from producing sound when a plug is plugged into the headphones jack. . If you have used the headphones jack a lot, it's common for that mechanical switch to malfunction. If you insert a plug into that jack and wiggle it, then pull it out, that may get one or both built in speakers to produce sound again, but the only lasting solution is to replace the headphones jack - laptop repair places do that frequently.|
OR - if you plug a pair of amplified computer speakers into that headphones jack, that will probably yield you sound.
If you HAVE loaded Windows from scratch since the speakers last worked, the drivers for your sound adapter are probably not built into the contents of the Windows CD.
Most Dell laptops I've seen that originally had XP on them came with a Dell XP Re-installation CD and a Drivers and Applications CD or DVD or similar when the computer was new.
If you have the Dell Drivers and Applications CD or DVD or similar, install the software for your sound adapter from that.
If you don't have that Dell CD or DVD, you must go to the Dell web site and find the software downloads for your specific model and download and install the sound software and install it properly.
While you're at it, you should install the main chipset drivers for your model, and after that the drivers for anything else listed in Device Manager that it shows you do not have the drivers installed for.
(e.g. RIGHT click on My Computer - Properties - Hardware - Device Manager.)