The built-in speakers on my HP w2408h do not work. I checked the sound generating electronics in my HP computer with a headphone. That worked. I plugged in the sound patch cord to the headphone jack in the front panel. The Control Panel Sound ap shows that the computer recognized the monitor's built-in speakers whether they are plugged in to the front or the back of the computer. They just are not producing any sounds when I test them or any other time.

Generally speaking, sub-woofers are not built into notebook computers, as most sub-woofers would not fit. However, there are generally speakers, and there tend to be problems with the audio drivers in most cases if there is no sound for both speakers and headphones.
Within the notebook, there should only be two speakers. If they're missing, did you buy this used or refurbished? If someone just yanked out the two speakers and carelessly cut or handled the wiring improperly, then this could interrupt the headphone bypass cut-off.
I know you mentioned you'd already verified everything appeared to be working properly, and in some cases updating drivers or uninstalling and re-installing them has a positive result. For the obvious, which I've also forgotten to check sometimes, is whether the output is muted within the volume control and mixer.
In case you hadn't already checked out these, here are a few links you may find useful:http://h10032.www1.hp.com/ctg/Manual/c01613382.pdf
http://h10032.www1.hp.com/ctg/Manual/c01613127.pdf

As always, the more complete the information up front, the better the potential for a solution. I hope this helps!

Have you checked the speaker settings? Make sure that all settings are NOT muted. One selection that is muted maybe where the sound is generated from. Such as MIDI playback. Otherwise it has to be either a missing update/driver or damaged speakers.

Apparently the built-in speakers have one bad. You can have the speakers replaced for you at a good computer repair shop if you cannot affort to send it in at this time.

Are you using external speakers? or internal?

EXTERNAL SPEAKERS: If your are plugging speakers into your headphone jack and they dont play, but you plug headphones into the same port and they work fine.. then it is the external speakers.

INTERNAL SPEAKERS: But if you are using the speakers in the laptop, then your speakers are probably bad. Try some software settings, but probly just bad speakers. Could also be that the speaker cord inside the laptop came unplugged from the motherboard. In which case you would have to take the laptop apart and plug it back into the motherboard.

Good Luck.

Try:
1. Check if the sound is on mute.
2. Click on Start and select Run. Now type devmgmt.msc and press enter. Check if the sound driver is not installed or has been disabled.
3. Check the speakers. Use external headphones, if the headphones are working properly, means the speakers of Laptop are damaged.

MUTE THE SPEAKERS SOUND

it sounds like the headphones shorted out the usb on your system, you might try some speakers that are not usb and see what you come up with,,,also check and make sur your sound isnt muted on the master control for the volume

Assuming your using a Windows operating system, you need to got to the sound settings and set your computers soundcard as the preferred output device. (Its under Control Panel > Sounds and Audio Devices in XP)

this plug is a INPUT no OUTPUT.

Looks like there is some problem with the stereo headphone connector. As its a hardware issue, I would recommend sending it to the service center.

You may also use external speakers temporarily.