PrimaVita said:
I had a earth elemental that attacked on my turn. On the computer's turn it played a Kor Hookmaster. It targeted my already tapped elemental, and made it not able to untap during my next untap phase. Am I wrong in how to play this card? Can you target a tapped creature to tap?
Unfortunatly you are wrong in how you play that card
http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=222763
Check the rulings on that gatherer page.
Im pretty sure it would only not work, if the card said something like "..cards tapped this way don't untap on their controllers next untap step"
There are other cards which are similar where you can use abilities even though you wouldnt think so, for example Garruk Wildspeaker, you can use his +1 to untap two lands, even if there arent two lands to untap, he still gets a +1 counter on him