Sound problem (no sound from int. speakers). Flummoxed.

Hi all, I hope you might be able to make one or two helpful suggestions to this. Thanks.

I've been sorting out a few things on a friend's laptop [running XP, SP3] & while I was there he mentioned that it wouldn't play sounds through the onboard speakers (although it did up until a few days ago & he's not aware of having changed anything & nothing new has been installed). External speakers plugged into the jackplug socket of the laptop play everything OK.

I checked the usual suspects; volume not muted anywhere, Device Manager says all working properly, latest drivers appear to be installed (SoundMAX; I clicked 'update driver' & there weren't any new ones found). This problem applies to system sounds (sound scheme is set as Widows default & highlighting, eg, default beep & clicking the 'play' button in the Sound Device Property box plays nothing) as well as to music stored on HD & to music CDs put into the CD Drive. All of these work perfectly through the external speakers, so I suspect a sound card problem is unlikely. I also clicked the 'Audio' tab from the Devices Property box & checked everything there, including the 'Advanced' settings. All seems as it should be. In the Sound Playback Advanced section, the speakers are correctly listed as Laptop Stereo, but I tried a couple of the other settings to see if they worked, but no joy.

Any suggestions for anything else? It's a fairly new machine, although out of warranty, & hasn't been heavily used so I hope it won't mean replacing the internal speakers. If that's the only option I'll suggest he goes to a shop as I've never dealt with the innards of a laptop before & am reluctant to use his as my first go.

There's no rush to get this done; my friend bought a laptop only because he doesn't have room for a desktop set-up & just uses it indoors so using the external speakers through the jackplug will do for now. However, I am his regular 'Mr Fixit' for most things computer-related (admittedly, most of them pretty straightforward) & so I would like to find an answer to this, if possible.

Thank you for taking the time to read this & I hope you can help.

Martin