Your now on your way up Ganon's Tower. Along your way up you'll run into two Dinolfos. Nothing different about them, so slaughter them and continue.
The next room has you fighting two Stalfos. Same old. In this room though you need to pick up the Boss Key.
You fight two Iron Knuckles in the next room. After that its up to Ganondorf.
If you at all remember Phantom Ganondorf, well, the real thing is practically the same thing with a couple of small changes. One difference is Ganondorf will pound the ground, altering the stage. The next is you don't have Navi to help you out.
Your waiting for Ganondorf to shoot a ball of magic at you. At that time you have to hit it back with your sword. Press B right as the magic gets close to you and you whack it back at him. Continue until it hits him and not you. Once he finally does get hit. He will be weakened but he's not done. Right then you have to hit him with a Light Arrow. Also, when he does his special black magic move you can stop it as well by using a Light Arrow. Once he goes down from the Light Arrow jump to the center platform and hit him with your sword. Actually, now that I just tried this, don't delay, just hit him with a Light Arrow. After a couple of whacks he's done.
After that it's time to follow Princess Zelda through the collapsing castle. Not much help I can give you here. Just always make sure your keeping right beside Zelda. Don't assume where she's going to go.
The Castle then collapses and you are out safe and sound. The game's not done yet I'm afraid. You hear a sound! What could it be? Run over and check, then click here.