IT WORKS !!!
I've copied tinycore again, checked its md5sum and this time it matched !
Now the computer boots and works like a charm !
Thanks a bunch guys for your help, it's very much appreciated
I guess I'll need your help again when I will set up the print server: CUPS + Foomatic + GUTENPRINT + PPD files = HELL ON EARTH
Bye and thanks again, Magic Sam