I am trying to train my thief into a Ninja. I am at the draw bridge at the old haunted castle, but cannot find a switch/device to lower the drawbridge to complete the quest. Does anyone know where it is or what I have to do to get the drawbridge down?

Okay the search was not working and I see that someone asked this a while ago. The switch is suppose to be on the right tower. Is it at the top where that spirit I killed was? Also, will it be there without having cleared the castle?

Yes, the switch is at the top of of the right tower. I think it's there regardless of whether you've completed the Castle. It's kind of hard to see, so you might want to use Spirit Eye to locate it.
--MisterDrgn

If you are standing outside the castle and facing it, it's the left tower. If you're inside the castle facing out the drawbridge, it's the right tower. Just climb up the staircase and make sure it's the ninja-to-be is the one who pulls the lever.

Try not to kill anything just to be safe. Incidentally, I found the invisibility spell fairly useful for this quest.