Hi, I'm Ashik. Welcome to JustAnswer. I'm reviewing your question now, and will post back with your reply ASAP
You can't drag and drop an Album from iPhoto to desktop. You need to do this way.
First create a folder on desktop and give it the album's name. Then open iPhoto, click on the album in left column.Select one photo in that album and press Command and A and this will select all the photos in that album. Then click and drag and drop them to the folder you created on desktop. Don't drop it on main desktop. Make sure you definitely drop it on the folder you created on desktop.
Please let me know if that didn't work, so I will continue to help you