Yesterday we deleted temporary files that were taking up too much memory. We
also "defragged" the computer (well, it wasn't me; I have no idea what
"defragging" does). Our antivirus software also found a potential virus, but
it seems as if it prevented the virus from ruining anything.

However, now there is no sound. We can play Windows Media Player and iTunes,
but the volume can't be used because of missing hardware. It's constantly
muted. the message says, "Multimedia audio controller is not configured
correctly" but we aren't able to reinstall, even if we use the installation
CD provided to us when we bought the compuer. We can't update the driver at
all.

Any ideas on where to begin?

Thanks