Mildew problem in A/C vents???

Any one having problems with Mildew in their HVAC?  My fiance has an '06 and the dealership is telling her that she has mildew growing.  The big frustration is that the dealership says that VW won't cover it under warranty (even though it's a lease) because it's considered to be "normal wear and tear" of the vehicle and it's past the 1 year 12,000 mile part of the warranty.
 
Suggestions on how to get it taken care of?  At least how I could treat the HVAC and get rid of the mildew problem?
 
Thanks!
PurduePete