Kirby's Return to Dreamland on laptop

Hello, all. I'm trying to play Kirby's Return to Dreamland on my Lenovo G570 laptop. I'm playing it in fullscreen so that it runs faster, and I've tried just about everything, even making the resolution smaller. So far, it runs full speed for around 20 seconds at a time, then goes to less than half speed for another 20 seconds.

Can someone help me out with this? I know my laptop's capable.