Okay.. I try again:
Converting the MP3 files
You need the MP3 files to be in uncompressed WAV format. The Cassini emu has a tool packed with it, called Saturn MP3-WAV converter. It's easy to use, just select the MP3 files you want converted (In the case of Panzer Dragoon, something like PD01.MP3, PD02.MP3... ) click the Add to job list button on the right, then MP3 -> WAV. Soon, you'll have the .WAV files. For some weird reason, this did not work for me, though.
So, an alternative method to convert the MP3s to WAV is using a free converter, like
dBpowerAMP. Install this little prog, and after that you can either start it up and then select the files that need to be converted, or open the folder where the files are, and select them. Right click, and there should be a new option, Convert to... Anyhow, now you need to set the output format. Select WAVE, 16 bit, 44100Hz, 2 channels, these are the defaults for CD quality. Click Convert>> to start converting.
Creating a playable image file
Now you have the audio tracks in WAV format, the rest of the data in an ISO. If you already have a proper CUE file, skip this part. You can use a proggy called
Sega Cue Maker to create a CUE file. Just put it in the folder with the ISO and WAV files, launch it, then input the name of the CUE file to be created (for example, Panzer_Dragoon).
Mount the CUE file with a virtual CD drive, like Daemon Tools. Installing this will create a small lightning shaped icon in the tray in the lower left of your screen. Left click on it, then select Device 0. Select the CUE file, and now it should be mounted. You should have a virtual CD drive, with the contents of the game. So that you can play it easily later, I recommend creating a proper CUE/BIN image. Get Alcohol 120%, it's a pretty decent disc copying program. Start it up, select Image Making Wizard, then select the virtual drive you've mounted the game to. Choose CDRWIN Image file as the image format. Once it finishes, you have a normal image file. You can either play this on an emulator, or burn it to a disc with the Image Burning Wizard function of Alcohol 120%.
OK ?