This is at the level of "Did you check to make sure it is plugged in?", but I have seen people go nuts checking for the underlying problem and the issue was that they had accidentally put the sound on mute. On my computer, the sound icon gets an X when it is on mute. There are several locations where you can disable the sound through a setting. If you didn't already check those, it's worth a look before you buy a new computer. If you are getting a message that "No Audio Output Device is Installed", it's not that.