It can be a pretty difficult quest. Run to across the river (use the fallen metal beams as a short cut) and use the hook to pull you up. Then just keep climbing upwards/around the windmill to advance upwards. You will need to use the windmill blades several times to advance to the next levels (jump and grab on the blades with the yellow wood) and then jump across to the next level. You will eventually make your way to the top to set the charge.
Of course, you can also use the CH trainer to teleport you upwards by adjusting the player "Y" position in the editor. Just be careful not to advance yourself so high above that you are out of the mission zone.
Video: www.youtube.com/watch?v=SSXvUupfd7w
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Old Villedor Master Windmill
wINDMILL 1
X 1716.92
Y 92.06
X 1325.50
wINDMILL3 1ST JUMP
X 1731.25
Y 101.07
X 1325.66
wINDMILL3 2ND JUMP
X 1725.50
Y 105.89
X 1327.43
wINDMILL3 3RD LAST JUMP
X 1717.52
Y 111.23
X 1323.42
OVM WINDMILL NEAR END
X 1715.83
Y 128.29
X 1324.77
TOP of Old Villedor Master Windmill END
X 1717.28
Y 140.37
X 1316.01
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