In a previous lifetime I was tech support guru for a sound card mfgr. So here’s my triage procedure for missing sound:
[li]Is your computer plugged in? Is it turned on (don’t laugh, it happens!)[/li][li]Do you have a sound card (not so much an issue these days.)[/li][li]Do you have speakers plugged into your sound card? (old-time computers didn’t output sound card sound through the built-in speaker; some new ones do)[/li][li]Check to see that your speakers are plugged into the sound card, into the correct socket. Yes sir, I KNOW you checked that, please check it again. Thank you. (Don’t get burned on this one, you’d be surprised how many times the customer swore it was plugged in…)[/li][li]Plug a set of headphones into the speakers and test the sound. If that works, check your speakers with some electronic device.[/li][li]OK, no sound from card period. Open your volume controls, turn everything up, ensure that mute is not set anywhere, check the advanced options.[/li][li]Still no sound. OK, let’s figure which sounds don’t play. First put an audio CD into your CD-ROM drive and play it (CD sound comes from the CD player and only routes throug the sound card’s mixer).[/li][li]OK, you have CD sound but no wave/MIDI sound. It’s either a driver problem or a card problem. For XP, not likely a driver problem unless you’ve installed some weird software lately.[/li][li]OK, you have no sound still. Hmmm. Most likely a bad sound card if the mixer isn’t working, but may also be driver. Only way to be sure is to test the card on another computer. If the sound chip is built-in (very likely on most modern off-the-shelf systems), 90% its the hardware.[/li][/ol]
Check the speakers before doing anything else. Then check the mixer (volume control); mixers are always getting reset. Figure out which type of sound ain’t working (CD, wave/MP3/etc., MIDI). Back when I was a boy (and programmed by candlelight), the problem was mostly that the computer was too underpowered to do sound, or the OS was screwed up. Any computer from the last 10 years has enough power, and any Windows OS (after WIN 3.1) is usually robust. That leaves dead hardware or weird interactions.
Sorry I can’t help Mac or Linux/UNIX users.