New computer sound problems.

Hey guys, I'm having a bit of a problem. I recently built my new computer a few weeks ago and ever since i've had it ( i use skype ) people on skype have been starting to complain about the loud sounds coming from my end like game sounds and music and such
They tell me to turn down my speakers but one problem... I'm wearing headphones..

so i did a little test so i unplugged all speakers from my computer and then typed to him and asked if he could hear my music and he said yes... and its not just him its other people also ..

How could this be happening unless my music is being streamed to him ...

Anyone have any ideas i'd like to stop this annoyance.

I do not have any internal sound cards.. its all through my motherboard but i do have front audio port. which is where i plug in my speakers

Go to volume properties, options, propertys, recording, ok, select only microphone

or you can disable the sound completely by muting it and then see if people can hear the weird sounds/music

select the microhpone tab in you sound properties..ebcause what i think is happening is that the sound that are suposed to come out of your computer speakers substitute for the microphone..so anything that comes out you speakers normally will be heard