When I roll my window down after a rain/snow storm there's streaks of water on the inside (different than the greasy streaks covered here before) and it smells like mildew.

Is there anything I can do about it?

Why is water on the inside and why isn't it drying out?

 

Take the door panel off and check out the inside. Then you might see what is causing it. Did you just get your MINI? Maybe the previous owner spilled something down the door when the window was open.