There could be a simple explanation for your problem, but nobody can help you unless you tell us more about your set-up.
If you download and run this free program click here you will then be able to tell us details regarding your Motherboard and whether you have a Sound card etc. What OS? is XP or Visa or what? What make webcam/mic ? We would have something to go on then.
OK - very often the Front usb ports are not actually connected to the motherboard - are you sure that your Front ones are connected? In other words, do any USB items work when plugged into the Front ports?