Mice are deceptive little buggers. They're so cute, but smell so bad. And a dead mouse smells even worse!
A mouse died in a closet in our old apartment, and I used Febreze on the area (after I made my husband get rid of the poor thing). To prevent mice from coming into your house in the first place, use peppermint. They say you can also use onion, but I don't suggest that unless you want your house to smell like an Italian restaurant.