I just got me a Wiikey.
 

And I just downloaded metal gear : the twin snakes for gamecube.

There are 2 folders

rks-mgsts1 and rks-mgsts2. The game has 2 disks so thats the folders for both disks.

In the 1st folder there are 2 files, one's an NFO file which is 5kb and the other is a MagicISO which is like 1,400,000kb. do I burn both to a dvd-r or just the ISO? Never had a modded console before so I don't know what to do.

Cheers

Just the ISO file. NFOs are just information files with instructions. Open the NFO in notepad and it should tell you what to do.

What he said. And if you ever get .gcm images for the Gamecube, just rename them to ISO.