Mildew can often be treated with cleaning products, leaving surfaces unharmed. Sometimes a good scrubbing bush is needed, too. I've been able to clean mildew easily many times using a solution of bleach and water. Mold, however, is a different story - especially if it has had time to grow further into surfaces. Mold removal is best left to experienced professionals as in many cases walls, floors, ceiling sections, and more will must be replaced. Mold exposure should be dealt with the right way too. For best results, if you have moisture or high humidity you can prevent mold by ensuring leaks or water sources are completely stopped or by using a dehumidifier.