Yeah but to cause headphones not to work too that would use a seperate connection than ones inside the laptop would of course use.
This tells me that you have a bad sound chip on that laptop of yours or it could be a number of the below things:
Though of course, onboard sound is never as good as dedicated external or internal boards like Creative.
Go into Volume Controls and if its not already set, go to Options, and accept Advanced Controls.
On some sound cards you'll get an extra function opening up saying advanced as a button hopefully under Play Control.
Check that the bass (if it has this) is set to around the middle, or 3 1/4 of the way up, and treble about in the middle or about the same (full is best for headphones since they have better bass response though it might mess up that onboard sound).
MICROPHONE (Might very well be it):
Next, check your microphone status in the volume control and mute it to see if this helps at all (it might be picking stuff up, causing the cracking and high bass)
If you can't see the volume of this to mute it, go to Options again, and open up Properties. Now select microphone from the checklist and press okay.
Now it should be there. Just simply mute it
Does this help? I hope so