In finder go to your "username" then to "pictures" where you will see "iPhoto Library", control click to bring up menu, click on "show package contents".
There you will see a folder called "originals" where you will find all your iPhotos. Just copy that folder to your desktop or anywhere you would like.
Now when you are in Aperture or any other program you now will have access to your iPhotos.
Hope that helps.
Ed