I have 37 stars and I cannot figure out how to get to the second floor..

To get to the second floor you have to beat the second Bowser, which you're having trouble with. To get to the second Bowser once you're in the level, you need to jump on the wire platform and dodge the stuff.

Head right past the enemies and climb on the pole. Jump off and go up the teetering platforms and up the next pole.

Go to the left and ride the elevator up. Head left again and make your way to the rising and lowering platforms. Go to the top and wait for the platform you're on to rise to the other. Walk on it.

Make your way past the platforms and the lava and run fast over the bridge (it collapses), and jump down the hole.

Bowser will tilt the platform at the beggining of the fight and when you throw him off the platform.

Just throw him into one of the spiked balls to win and get the key to the second floor.

I know what you mean. Look, do you need help on beating Bowser or getting to him? Because when you beat him, he gives you the key to the second floor.

You can beat him like you did the first time. Simple.

Be sure to grab any 1-up Mushrooms you find. An easy way to do this is to go to Whomp's Fortress, make yourself a giant using the bricks near the Thwomp.

Then busting the Thwomp, jumping off the edge, wiping out the Bullet Bill cannon and the bricks, and clearing the pegs and Piranha Flowers, and you'll get lots of extra lives.

You have to use a regular link cable,the wireless ones doesn't work.

To get to the second floor, you need to beat bowser first and then he will give you the key.

To beat bowser, just do what you did when you frist beat Bowser, just grab him by the tail and throw him at one of those spiked-bombs.

Simple as that.

I agree with actionshark because that's what I did!