New technology - is it worth the hassle?

Hello - Hazel here learning yet more technology. I have recently bought a new computer and if anyone can tell me why my sound isn't working please do so!!! It was working the other day - has Limewire blocked it? I've tried speakers via a usb (they were previously working) and via my screen (previously also working). I even rebooted the computer and got the sound back but it has gone again saying my machine doesn't have any sound facility connected. It's an emachine. I've looked at self help, web site help to no avail. Any ideas please? It's driving me mad.