Hello Ernest,
> First, my PSR9000 can't read the styles disk that is shipped with the keyboard.
> 'Unformatted disk' error message. That can't be right my PC can read the disk and
> list its contents.
>
Can your keyboard read another floppy disks formatted with a PC? If no, your floppy drive is probably faulty.
Try to copy some styles to a DOS formatted floppy disk and it should be read by the keyboard.
> Second, HD disks formatted on PSR9000 only have a capacity of 720K, and once formatted
> on PSR9000, they can't be read by the PC. Why?
>
720K?????
How is the size of your harddisk? Did you mean harddisk (HD) or floppy disk (FD)?
As I know there are some problems with the current OS version and harddisks, but mine was formatted correctly to 2 GB (PC could not read it, but that was another problem).
Regards
Marek