Skype is still telling me I have no microphone

I installed skype today and realise from previous help that my Dell Inspiron 6400 does not have an internal microphone. SO i went out today and bought the Microsoft LifeCam VX-5000 I installed the programing including messanger which I hate, but when I go back to skype I am still told I do not have a microphone,. This is driving me crazy I have little patience with computers at the best of times, NOW I think I'm getting close to throwing it out of the window HELP PLEASE
Wendy