One speaker on my computer isn't playing...
 

...and I don't know why. I recall it working a couple of days ago, but I've installed a whole bunch of stuff in the meantime.

I'm on a WinXP Pro machine, with external speakers. If I plug the speakers into an external source (my iPod), I get sound from both speakers. But through the computer, only the right speaker works. This is the case through iTunes, WinAmp.

I've tried Control Panel > Sounds and Audio Devices Properties, and the balance is centered on that; if I drag it back and forth, my right speaker goes in and out, and the left remains silent.

Any other ideas?

have you taken your headphones and listened to the speaker port directly? maybe that's were the issue is.

I agree check the computer with anouther device (headset)....
Is there a line out as well as an amplified output...

One more thing to try is use Knoppix to see if its a driver/setting problem or if its hardware related

It probably is the headphone jack. Alot of the jacks are real chintzy and can break easily, and the only way to fix it most of the time is with a little soldering.

Do you have a sound card installed on your computer? If so ensure that the settings for that are set correctly for two speakers and that your audio is set to use the sound card.

Also, if you do have a sound card, try plugging your speakers into the motherboard speaker port and see how it works.

That's incredible, I was just about to ask the very same thing. I recently upgraded to a new motherboard, and my speakers are doing the same thing as redlemon's. I'm using XP pro, and the left speaker(external)will not work.
I've tried everything recommended, and nothing seems to work.

double check that the speaker cable is plugged all the way in....?

And I come in this morning, and everything is back to normal. Weird. Sorry to bother everyone, thanks for all your efforts.

THIS IS WHY I LOVE WINDOWS!!!! ;)

Although to be fair, Linux has given me a few "Hunh. Now it works. Weird." moments too. But usually only as I set something up and I'm learning to configure it....

I wasn't going to mention how I have way fewer problems on my Mac at home, as opposed to the Windows at work. And, I run the network (~25 users) at work. But since you brought it up... :D

Dude!! I had this same problem like a week ago. Using XPPro, all the sudden left channel went out. I thought for sure it was a cable problem so, I tried and tried to figure it out ... to no avail... Then for some reason I updgraded by audio card drivers (SBLive5.1) and it started working again! WTF is up with that?!