Dolphin "Couldn't Recognize" ISO

[Mario Murderer]

Hey everyone.
I've been having real difficulty trying to download a working ISO of Sonic Adventure 2 Battle.
So far, yesterday, the download seemed to have stopped twice (maybe that was my fault) but after I let it run the third time the ISO downloaded successfully. This is the file.

Sonic Adventure 2 - Battle (Europe) (En,Fr,De,Es).7z

I downloaded it from here.
When I open the ISO up in Dolphin (3.5), a Warning message comes up saying "Could not recognize ISO file, users/documents, blah blah blah". When I open up the program on my computer I get this message

Is a .7z file even an ISO file at all?? I downloaded Zelda: The Wind Waker several days ago with no problems and it was working fully functionally.

OS:

Mac OS X Version 10.7.5
Processor: 2.4GHz Intel Core iS
Memory: 4 GB 1333 MHz DDR3
Startup Disk: Macintosh HD

I have no idea what a MOD is so i'll just say i'm running this thing on Dolphin 3.5
I don't use burnt discs, because I presumed it would work on my computer as the last download did. My burner is built in with my mac
I don't use any plug ins for my emulator.
I will try an other ISO rom of the game later
Please i'd loooooooove to play Sonic Adventure 2 Battle at home again! I only have the real american copy that doesn't play on Australian Gamecubes!!!!

[deadlegion]

It's an archive.
Extract the .7z file using the latest version of 7zip (it's freeware).

[47iscool]

I Think Mac & Linux Versions Of Dolphin Have More Problems Than Windows Versions
You Can't Use The Gamecube's Bios IPL.bin On The Linux Version It Just Stops

[Mario Murderer]

I GOT IT WORKING!!! I downloaded another file and then extracted it, this time it let me do it and then the ISO worked!!!! YAAAAAAAAAY!

[47iscool]

Also Make Sure You Have The Latest Version Of 7-zip,Some Older Versions Won't Extract
Newer Files.