Help :(

[essex boy luke]

Right guys and girls I'm useless with pc's all i do is wreck them, right well my friend gave me a vista home basic disk after losing my xp one. every since iv plugged in two different sound systems and the pc hasn't picked them up, theres a little red circle with a white cross threw the middle and when you hover the mouse over it says 'no audio output device installed'.
would love some help on this one thanks