Upgrading a laptop processor

Have a Dell Inspiron B120 running with a Celeron 1.4 MHZ processor.

I was looking around on the net for possible upgrades.

Is there any rule of thumb when trying to upgrade.

I can find plenty of processors out there that are a physical fit (478)
Same Bus speed but I would like to get a little more out of this machine if possible.

I have seen P4's for 40 bucks new that match the specs but one of the concerns I have is about the what I believe is referred to as 'manufacturing technology."

My processor is a .13 I believe.

Do I have to pick a processor with that same spec? Or is that not big of a deal.

sure did

Celeron M that is

oops

alright, clowns get back in the car. To prevent you from doing something stupid, NO, a Pentium 4 cpu will not work in your B120. Intel had three socket 478s (actually 4, but one was named socket 479 despite using only 478 pins), a desktop version called socket 478 that Pentium 4 CPUs used, and two special mobile socket 478s, also called socket M and socket P. Let's not confuse this socket M or P with the Frankenstein laptops running desktop pentium 4 socket 478 CPUs back in 2002-2003. Socket M is a last generation mobile socket, being replaced by socket P, which ironically also has 478 pin cpus, but the missing two pins on the cpu are in a different location, making it impossible to plug a socket M cpu into a socket P socket. Okay, you can safely forget all that crap above. All you need to know is that you need to find a socket 479 processor. pretty much any Pentium M will do, but to be on the safe side I suggest you find one with a 400MHz fsb. Unfortunately, your laptop will not work with Core Duo or Core 2 Duo or Pentium Dual Core CPUs. A Pentium M cpu is as good as it gets for you I'm afraid (note it's "M" and not MOBILE, there is a big difference between the two. You want the CPU with the RECTANGULAR chip in the center, not a square).

Here, I'll get you started:
http://cgi.ebay.com/INTEL-PENTIUM- [...] 7C294%3A50
That one should work. Good luck.

P.S. BTW, your Celeron is actually 90nm technology, aka Dothan, and not .13 micron technology (aka Banias). Not that it matters much, but as my handle suggests, I'm a stickler for the facts.