My apologises for the late response! It is a desk Dell computer, operating system XP. I was given the computer by my daughter and cannot remember if there was sound when I first had it! I believe I do get sound when I play a CD but otherwise I don't appear to get any other sound at all. It has been unplugged and and reconnected since I have had, could I possibly have put a wrong cable in the back?
Welcome back! You will find two small sockets on the back, coloured green and pink. The lead from the speakers should be in the green one. If that's OK, it will be worth looking at the sound settings. Have a look and come back to us. By the way, are the speakers built in to the monitor, or are they separate?