My PC speakers aren't working. No idea why!?

Tried to fix it myself but to no avail. Bit of info Logitech - Surround Sound Speakers Z506 Windows Vista Home Premium Dell XPS XPS_40 INTEL(R) Core(TM)2 QUAD CPU 32-bit Operating System Stigma tel High Definition audio Codec Sure not all this info is needed but i will write it anyway as i have no idea Had a problem with my Logitech wireless mouse and keyword which i managed to fix but straight after my Logitech (non-wireless) speakers stop working. No idea why and never happened before so tried to learn and fix as i went Plugged in headphones that i know work and they didn't work either in the Pc so probably not the speakers I checked all the connections, plugs of the speakers and all fine The Digital output device is turned all the way up (whatever the name of the sound volume on your computer is called) I read some things and went into Device manager, Sound, video and game controllers and tried to download another Stigma tel High Definition Audio Device (this is the driver???) but when i went on it again there was an exclamation mark next to it and there was an explanation why it wasn't working now. (can't remember what it was) but it wasn't there before I then tried to Update it but my computer said i had the best driver software installed I then uninstalled the Stigma high def audio codex (was this a bad decision?) and i have tried download some other things but to no avail. Any help would be great as everything i try to read about it is far too advanced. So if you can offer some help please write it simple step by step like you are explaining it to your grandma!! Any help appreciated