Hi there
Welcome to the HP Support Forums! It is a great place to find the help you need, both from other users, HP experts and other support personnel.
Please post the full product number and verify the operating system in use on your notebook. See the following, if you need help with that information.
How Do I Find My Model Number or Product Number?
Is the Windows Version on My Computer 32-bit or 64-bit?
I understand that you are having trouble with the sound coming from the speakers when headphones are plugged in. I am happy to help.
Start with this page, and make sure that the headphones are the default audio device when plugged in.
Resolving Headphones and Headset Problems (Windows 8)
This covers some of the same but has a few other things you can look at.
How prevent sound from playing through both headphones and speakers - answers.microsoft.com
I hope this helps.