And find YOUR cpu, then compare it's "type" eg. 478-pin Micro-FCPGA
knowing the SSPEC ID of the cpu greatly helps. You can literally find it if you take your laptop apart, there might be some info on google about it though.
Another way to find your cpu 'package / type (the if it fits part) is using a program called cpu-z or cpuid, they're pretty good at telling you what you have in your mobo and what your cpu is.
Another cpu that fits MUST have this same type as your cpu currently in there. And your northbridge / fsb should be similar and at 'least' supported. You'll need to do research to find our if your bios will support it. Then it's a simplistic matter. The latest bios is always pertinent to have flashed on your mobo.
I'd find out the top FSB that your northbridge / chipset can support and only get a pentium with up to that.