Why do i have allot Of back ground noise on my laptop when i voice chat?

hello i just got a gateway laptop and i do voice chatting on there threw skype and my friend was telling me he gets allot of back ground noise i do have a built in microphone that dose not work well but use my microphone and still gets lots of background noise how can i fix that but when i go on my desk top he dose not hear back ground noise thanks so much. it is a bran new laptop