Unknown File .GRP. How to Open it?

Hi, I've been sneaking on my wii game for some music , but I found it on this type of file with extension GRP. I've been searching on the net, but the only info i've got is that this extension is used in a game with a tool called Duke Nukem 3d archiver. I tested it, but doesn't work.

Any Ideas how to open it?. Just for the case I found it on the game Code Lyoko Quest For Infinity PAL with the trucha signer.

dude, don't post the same question in two places... I answered in your other post...

mod please erase.