I didn't really get the ending (spoilers)

NOTE: I'm talking about the normal ending, not the fancy one.
Okay, I just beat Ansem, the easiest boss ever. yay? I dint get it really. Riku goes with Mickey do to.....whatever they were gonna do. Then Sora goes to Kairi and they get seperated. You see Kairi on her Island and she goes to the secret place. She sees the picture sora drew of them sharing that star fruit, and then she starts to cry and... the credits roll. During the credits my PS2 decided it hates me and it froze. I took the game out washed it, put it back in and the game went back to the title screen automaticallly. So I broke my controller and flipped off my PS2 for a little while realizing that the last bosstook me 45 minutes.

Okay could someone explain to me this whole thing?

Well, you missed the final video, which shows what Sora, Goofy, and Donald do once Ansem is defeated (this is not the special ending, just the last bit of the normal ending).

Anyway, Riku and Mickey get trapped on the other side of the door to darkness. Sora runs to Kairi, but they get seperated. Kairi returns to the islands, and she explores the secret place, where she and Sora drew as kids. Kairi sees the drawings that she and Sora made of each other, and sees the paopu fruit that Sora added, which is why she cries. She then adds in her giving a paopu to Sora as well.

After the credits, we see Sora, Donald, and Goofy walking along a dirt road.
Donald: "So now what do we do?"
Sora: "We gotta find Riku and King Mickey."
Goofy: "But where do we start looking for that there 'door to the light'?"
*All three sigh and hang their heads when they realize they have no clue. Then Pluto shows up, with a letter in his mouth marked with the king's seal*
Sora: "Do you know where King Mickey is?"
*Pluto runs off. Donald and Goofy grin at each other, while Sora starts chasing after Pluto, then stops and calls back to Donald and Goofy*
Sora: "Guys, let's go!"

This sets the stage for Chain of Memories. I don't think that the quotes are exact, but they are the best I could remember without watching the video again. Basically, Riku and Mickey get trapped behind the door to darkness, so Sora and company decide to go after them. Kairi winds up back on Destiny Islands, where she is currently waiting for Sora (and Riku, probably) to return.

how can someone take 45 minute to beat the final boss? well maybe if all the final bosses after the last rest but still i don´t think it takes 45 mins..

Like Skyblade said, you missed the video that makes you kinda understand it.