How to fill PSR8000's hard drive easily?

I've just upgraded my PSR8000 with a toshiba harddisk and it's working fine. I wold like to copy 2000 or more midifiles (from a CD) to it without using floppy disks so I connected the hard disk to a PC and copied the files. Unfortunately my 8000 can't see the files copied by the PC, only the files I created with the synth itself. Does anybody know an easy way to fill the hard drive?
I also have 600 style files to load. Thanks in advance for any help.

Since then I discovered that the PSR 8000 creates a special directory structure, renames songs and saves song information (like original filename)to an *.mng file. Is there any PC software to model this in order to copy that many files quickly?