Bud
I think the S550 and the S330 work the same in this respect. There are two disks needed. one is the system disk, used to boot up the unit. The other is the UTILITY Disk, used to make samples. You can download the disks from http://w30.msoft.it/s550.html. I understand that the file called system is actually the utility disk. You also need to use SDISK to set them up for use. If I'm in error here, I am sure that someone will correct me. If you have no success with the download let me know and I can email the Utility file from my S330 to you and see if that works with your S550.
Also check the reply from Mgomes in the "S-50 OS" 11/27/99 posting in this forum for another source for the system and utility disks. (I actualy think the name screwup is at this location, not the one I listed.)
Majik

[This message has been edited by Majik (edited 12-02-1999).]