To clarify: A PND can be either an ISO or a squashfs file (and in the future, other formats might be possible too). The mount command that ED gave above should work for any case on Linux (and Mac maybe?), but on Windows will be tougher. If it's an ISO-based PND, you can rename to .iso and mount it with Alcohol or Daemon Tools or whatever; if it's squashfs, you'll need to get squashfs-tools for Windows (which I am having trouble finding, but it looks like there's one
here).