The GameCube emulator for PC is called Dolphin, it doesnt work so great, and it hasnt been updated since 04 i think, ill find a site now, but dont get your hopes up
the engine the GC uses is so different from normal hardware it is superhard to get the graphics emulated right, for ex. the colorful boxes on Super Mario Sunshine CANNOT be emulated correctly, anyway if you wanna check it out ill find the site
EDIT:
its here and they JUST released a x64 bit version, after 2 years of inactivaty, lol