A friendly FYI--You have a
MacBook or
MacBook Pro; PowerBooks have non-Intel processors so could not run Osirix. Functionally, they perform equal to Intel Mac Minis, but the Minis were released before the MacBook lines, so your conclusion may indeed be correct.
OsiriX requires an Intel processor and the Mac OS version 10.6 or 10.7 (referred to respectively as, Snow Leopard and Lion)
To Wobbly- Early Mac Minis had G4 processors, later Intel "Core Solo"/Duo/i3,etc.