You can set up IK for it in the Hierarchy editor easily enough.  Look for "IK chains" under the alien's body parts and click on it. That should un-gray out the "Create IK chain" button. which you then click and name it Left Hand (or Right). Then you should have a new IK chain available to you. Now simply drag the parts of the arm starting with the collar (or whichever part is furthest from the hand) and drop it onto you new IK chain. Repeat until you finish with the hand. Now you should have IK available in the Figure/ Use IK menu.

Save just before you do this as sometimes this can cause unexpected results if the figure isn't properly set up and this process is not undoable.

Don't know why you can't drag in the hierarchy editor. Perhaps that's new in 7 but I don't think so. Test it out with a primitive such a ball. If it works with the ball, then there is something wrong with your brain - and I mean that in the nicest way possible :)

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