Centrino ha tenido hasta ahora 5 familias, y la sexta que ha sido introducida hace poco.
La primera Generacion (Carmel):
CPU: Pentium M Banias/Dothan Chipset 855 Socket 479
La segunda Generacion (Sonoma):
CPU Pentium M Dothan Chipset 915 socket 479
La tercera Generacion (Napa)
CPU Intel Core (Yonah)/ Core 2 (Merom) Chipset 945 Socket M
Aca lo podes tener un poco mas claro:
http://en.wikipedia.org/wiki/Centrino#Carmel_platform_.282003.29
http://www.cpu-world.com/Sockets/Socket%20M%20%28mPGA478MT%29.html
Pero si tu micro es Yonah, entonces es socket M, igual si revisas no hay celerones M 420 para socket 479
Con la confucion del 479, creo que esto lo explica:
The Yonah socket is still a 479-pin interface, however the pin-out has been changed once more, and of course Yonah won’t even physically fit into any current Pentium M motherboards. Instead, you’ll need a brand new motherboard with a brand new chipset. So if you invested in any of the handful of desktop Pentium M motherboards that were released over the past year, you’re unfortunately out of luck.

http://www.anandtech.com/showdoc.aspx?i=2627&cp=6
Aunque si pusiera la captura del CPUz ayudaria bastante, en la primera pagina sale el pin count