You could put OS 9.0 on there if you wanted.
You really don't, though.. sluggish doesn't even begin to describe it..
9.1 (the max - I did try the Tiger CD in it once to see what happens, but you just get a Sad Mac...
) works on the one I have, but they're not great machines and will never be what one might describe as "fast" - the OS itself is not too bad (after waiting several minutes for it to start up), but apps are slow on it. I can browse the web and everything on it, but that is very slow too. The built-in graphics are absolutely horrible though, I would want at least an AV card if I was going to use mine.
