I do not believe that Celeron CPU would be supported by anything except possibly Snow Leopard. Or maybe with a custom kernel, like for Atom CPUs. From Lion, Mac OS X requires a Core2Duo minimum, and Celeron are below that minimum spec, as are dual core Pentium as far as I know. What you could do though is try out retail SL 10.6.0/10.6.3/10.6.8 with Nawcom's ModCD and see where that leads you.