Laptop Dj Case

HELP! Why is my speaker echoing through headphones?
I have a Dell Inspiron 8100. When I plug in my headphones, to listen silence to music, the music sounds echo, as if listening to be recorded in a studio. However, when I can remove my headphones to my laptop the sound is fine, no echo. What could be the problem and how I can fix it? Being a DJ I possibly could be blown speakers on the laptop, but this can not be the case. It could be just a problem of solving simple problems. HELP!
Muting the microphone handset (assuming yours has a microphone).
Swanflight Coffin Case Custom Built for CDJ-400′s, DDM4000 & Laptop