Hello,

> I'm out of luck today. The boot floppy says this Mac isn't supported,
> what should I do now ? I'm clueless.

Oops, that's bad. I seriously thought it would work on an S900, it's supposed to boot on anything between 68030 and old-world PowerMacs. What kind of processor do you use? Maybe it doesn't like G3s. I'm pretty sure I used this disk on my S900, but back then it had 2x604e...
I guess your best bet is a MacOS CD.

have fun
Michael