It could be a variety of issues, i.e. perhaps the speakers are going bad, a bad speaker controller on the motherboard, or the cpu is lagging a bit when it comes to controlling the sound, etc... It's strange that the headphones work alright, but not the speakers, hence the conundrum. I'm a bit stumped myself. I'd try contacting HP/Compaq support and see what they have to say- perhaps it is a relatively common issue that they have a fix for.