Whats wrong with my laptop mic?

i was recording a video of me singing on youtube and i did that like ten timess (i couldnt get it right :P ) but then i recorded it again and when i played it back it was echo-ing like crazy so i tried again and the same thing happened so then i signed out and signed back it but still the same thing. i then tested it with skype and it was perfectly fine so i did it again on you tube and again it was echo-ing when i played it back so i tried windows movie maker and when i played it back it was echo-ing AGAIN! whats wrong with my laptops mic? why is it doing thiss? thankss :)