NO AUDIO in MSN Instant Messenger! HELP

Hello, I am not able to hear the person whom I have asked to accept the
audio when I am using my MSN Instant Messenger. Nor can they hear me!
Can someone please tell me what I can do to trouble shoot this and find the
solution. My mic DOES work, because I was able to
use it to record a message in my Incredimail E Mail Programme. Also my
speakers ARE working. My computer is only 1 month
old and the best Dell sells. Can someone please help me so I can talk to my
mother on the mainland? I am in Hawaii, and my neighbor
talks to her financee all the time using their mic's crystal clear. I have
Road Runner for my ISP. My computer is only 1 month old and is a Dell

Thank you Henry