My computer speakers are plugged in and not working?

the green light is on and everything. My father recently wipped out my whole computer, because I had a huge virus and now my speakers do not work and everything else does. I believe the brand is e-machines. I'm only 15 and I don't know much about this stuff lol. Uhmm I can't ask my dad to do it causeee hes a busy guy so please help meee :] <3