model number is always important and pretty much all the early PIII can't be upgraded to much, if you can find a faster cpu from a sony laptop in the same model class (Like for example I have a PCG f480, there was also a 490 with a processor that was 50MHZ faster, I could technically upgrade to that. Or if you have a PCG F420, you could upgrade to the processor from a PCG F480 or F490). This is the most likely case and much more guaranteed.