you have to go on the fan blades of the mill and spin them counter clockwise
you open the top of the windmill by jumping on the the things outside of the windmill go conter-colock-wise and the top of the windmill will open. But, first before you do that you have to go inside the windmill and go to the top, past the girl dressed in black, and jump on the rope. THEN it will let you spin the windmill by jumping on it.
Open the door.
you jump up on the windmill and it will spin it clockwise. keep doing it until the little dome on the roof is open.
You talk to the guy outside the mill and he will give you some manuar. Then, make the windmill move and the opening will open, but make sure it is all the way open. the you click use on the manuar and it will power up.
Click on a book and it will open the secret door
you need to save all the nights then go to a secret place then open the kep and you have to bomb him
Assuming that you have released the gear lock inside, and the windmill arms are turning, the only reason would be if it is turning the wrong way : it has to go counter-clockwise to open the dome.
jump on the wind mills until the door on the roof opens. but first, you must go inside and unlock the gears by jumping on the white rope near the ceiling. you must spin the mills Counterclockwise.
When you get the windmill open on astro knights, you go inside and get the (manure-powered) hovercraft.
tou need to get a key
There is no key. Release the gear lock, then go outside and climb on the windmill arms, turning them counter-clockwise. This will open the roof dome.
You have to turn it counter-clockwise!!!!!!!!!!