I have trawled Google for hours looking for this problem. I was trying to unpackage a .daa disk image created in PowerISO on Windows. I didn't want to pay for the PowerISO application for Windows (and my file was over 300MB, which is the limit for the trial), so I was hoping to find a Mac alternative. Pages and pages of Googlism later, and I found the open source (GPL) DAA Converter.DAA Converter converts the archive to an ISO disk image format that you can mount in OS X. It's working great on Leopard, and I can't see a reason it shouldn't work on Panther or later, as stated on their page.

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