I have an HP Pavilion dv6000 laptop with Windows Vista. Just recently, I've had a problem with my headphone jacks. When I plug in my speakers, the sound still comes out of the laptop speakers, but no sound comes out of the headphones. Usually, when I plug in my headphones the Realtek HD Audio Manager pops up and says that an audio device has been plugged in, but that doesn't happen anymore. I originally thought there was a problem with my headphones because my laptop is 6 months new, and my headphones are cheesy 99 cent old ones. So, I tried my roommates' and his didn't work either.
I have the HP Pavillion dv6000 with Vista that had the same headphone jacks and speakers problem. I managed to resolve the issue by running the HP Health Check which brought up the update for Realtek Audio. Run the update and reboot the machine and hopefully your problem will go away too.
After following the steps there, I discovered that I didn't have the option to roll back the driver for my Realtek Audio device. If you find that you're stuck there as well, try this:
On the 'Driver' tab in the same Properties window as the 'Roll Back Driver' option, click on 'Update Driver' and see if there's an update that can be applied to the device. I've got mine installing right now...so hopefully that puts an end to things.
Hope this helps! These little things are so frustrating sometimes.