Opening .PAK files

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I'm trying to rip game music from a .pak file but have no clue how to actually get inside the file. I've tried wally, pak explorer, and pakscape, all of which gave errors and couldn't open the file. The pak file is from Disgaea; I'm trying to rip or downsample some of the music so that it'll fit on a CD.

Does anybody have any clue what program I'm supposed to use to open the file, or what the problem is?