Secondly what should be my next move with the non-functioning 100GB DMS - I couldn't find an explanation about DMS repair does - is it unwise to run this on my 100GB DMS. If I can get my 20GB DMS backed up maybe I could take this risk. Any help or advice welcome. Thanks
If you want to run the backup process, then make sure you are running the tools with elevated permissions (Run As Administrator). You should do this under Vista/Windows 7 anyway if you have not disabled UAC (User Access Control).
The disk access process will likely need this to function correctly. In reality the only thing you ever want is the disk signature (I might have called it boot block for the tools purposes), and the hack procedure does this for you too. To date, I've never had anyone ask me how to restore from a 'backup' for a legitimate reason.
As for the DMS that is not working, I'm presuming you fixed the DMS from a music point of view by re-running PhatMac and re-adding media?
If not, you should do this first and try booting again. With a power failure before the application has completed writing to the DMS it could well just be that you don't have valid 'index files' that the box uses to navigate the media.
If you have, then it's possible that there is some form of file corruption on the PHTSYS partition. Running the DMS Repair (PHTSYS) will format that partition, re-download the selected firmware and system files, and populate the system partition correctly. Remember to uncheck the option 'Reflash box', and if your box is not hacked be sure to use the option 'Install non-hacked firmware'.