i cant get dolphin to play the gc rom i downloaded. plz help

[shadowecho02]

i downloaded the dolphin 4771

and i downloaded a rom of pokemon xd but it won't play. its even an iso file. plz help.

it says the file is invalid

this is the file as it is now :

Name Date modified type Size
Pokemon XD 07/03/2010 3:35PM NTI iso file 32 KB


Please help if you can